Let's define a forest as a non-directed acyclic graph (also without loops and parallel edges). One day Misha played with the forest consisting of n vertices. For each vertex v from 0 to n - 1 he wrote down two integers, degreev and sv, were the first integer is the number of vertices adjacent to vertex v, and the second integer is the XOR sum of the numbers of vertices adjacent to v (if there were no adjacent vertices, he wrote down 0). 

Next day Misha couldn't remember what graph he initially had. Misha has values degreev and sv left, though. Help him find the number of edges and the edges of the initial graph. It is guaranteed that there exists a forest that corresponds to the numbers written by Misha.

Input

The first line contains integer n (1 ≤ n ≤ 216), the number of vertices in the graph.

The i-th of the next lines contains numbers degreei and si (0 ≤ degreei ≤ n - 1, 0 ≤ si < 216), separated by a space.

Output

In the first line print number m, the number of edges of the graph.

Next print m lines, each containing two distinct numbers, a and b (0 ≤ a ≤ n - 1, 0 ≤ b ≤ n - 1), corresponding to edge (a, b).

Edges can be printed in any order; vertices of the edge can also be printed in any order.

Examples

Input

3
2 3
1 0
1 0


Output

2
1 0
2 0


Input

2
1 1
1 0


Output

1
0 1

Note

The XOR sum of numbers is the result of bitwise adding numbers modulo 2. This operation exists in many modern programming languages. For example, in languages C++, Java and Python it is represented as "^", and in Pascal — as "xor".
import java.io.*;
import java.util.*;
import java.math.*;

public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		OutputWriter out = new OutputWriter(outputStream);
		Task solver = new Task();
		solver.solve(1, in, out);
		out.close();
	}
}

class Task {

	public void solve(int testNumber, InputReader in, OutputWriter out) {
//		TreapSet<IntPair> set=new TreapSet<IntPair>();
		TreeSet<IntPair> set=new TreeSet<IntPair>();
		int n=in.readInt();
		int[] xor=new int[n], degree=new int[n], arr=new int[n];
		for (int i=0; i<n; i++) {
			degree[i]=in.readInt();
			xor[i]=in.readInt();
			set.add(new IntPair(degree[i], i));
		}
		List<IntPair> list=new ArrayList<IntPair>();
		while (!set.isEmpty()) {
			int d=set.first().first, u=set.pollFirst().second, v=xor[u]^arr[u];
//			System.out.printf("%d %d %d %d %d %d %d %d %d\n", d, u, v, xor[u], xor[v], degree[u], degree[v], arr[u], arr[v]);
//			int x=in.readInt();
			if (d==0) continue;
			list.add(new IntPair(u, v));
			arr[u]^=v;
			arr[v]^=u;
			degree[u]--;
			set.remove(new IntPair(degree[v], v));
			set.add(new IntPair(--degree[v], v));		
		}
		out.printLine(list.size());
		for (IntPair i: list) out.printLine(i.first, i.second);
	}
}

class InputReader {
	private boolean finished = false;

	private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar;
	private int numChars;
	private SpaceCharFilter filter;

	public InputReader(InputStream stream) {
		this.stream = stream;
	}

	public int read() {
		if (numChars == -1)
			throw new InputMismatchException();
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}

	public int peek() {
		if (numChars == -1)
			return -1;
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				return -1;
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar];
	}

	public int readInt() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public long readLong() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		long res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public String readString() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		StringBuilder res = new StringBuilder();
		do {
			if (Character.isValidCodePoint(c))
				res.appendCodePoint(c);
			c = read();
		} while (!isSpaceChar(c));
		return res.toString();
	}

	public boolean isSpaceChar(int c) {
		if (filter != null)
			return filter.isSpaceChar(c);
		return isWhitespace(c);
	}

	public static boolean isWhitespace(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	private String readLine0() {
		StringBuilder buf = new StringBuilder();
		int c = read();
		while (c != '\n' && c != -1) {
			if (c != '\r')
				buf.appendCodePoint(c);
			c = read();
		}
		return buf.toString();
	}

	public String readLine() {
		String s = readLine0();
		while (s.trim().length() == 0)
			s = readLine0();
		return s;
	}

	public String readLine(boolean ignoreEmptyLines) {
		if (ignoreEmptyLines)
			return readLine();
		else
			return readLine0();
	}

	public BigInteger readBigInteger() {
		try {
			return new BigInteger(readString());
		} catch (NumberFormatException e) {
			throw new InputMismatchException();
		}
	}

	public char readCharacter() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		return (char) c;
	}

	public double readDouble() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		double res = 0;
		while (!isSpaceChar(c) && c != '.') {
			if (c == 'e' || c == 'E')
				return res * Math.pow(10, readInt());
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		}
		if (c == '.') {
			c = read();
			double m = 1;
			while (!isSpaceChar(c)) {
				if (c == 'e' || c == 'E')
					return res * Math.pow(10, readInt());
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				m /= 10;
				res += (c - '0') * m;
				c = read();
			}
		}
		return res * sgn;
	}

	public boolean isExhausted() {
		int value;
		while (isSpaceChar(value = peek()) && value != -1)
			read();
		return value == -1;
	}

	public String next() {
		return readString();
	}

	public SpaceCharFilter getFilter() {
		return filter;
	}

	public void setFilter(SpaceCharFilter filter) {
		this.filter = filter;
	}

	public interface SpaceCharFilter {
		public boolean isSpaceChar(int ch);
	}
}

class OutputWriter {
	private final PrintWriter writer;

	public OutputWriter(OutputStream outputStream) {
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(
				outputStream)));
	}

	public OutputWriter(Writer writer) {
		this.writer = new PrintWriter(writer);
	}

	public void print(char[] array) {
		writer.print(array);
	}

	public void print(Object... objects) {
		for (int i = 0; i < objects.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}

	public void print(int[] array) {
		for (int i = 0; i < array.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(array[i]);
		}
	}

	public void print(long[] array) {
		for (int i = 0; i < array.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(array[i]);
		}
	}

	public void printLine(int[] array) {
		print(array);
		writer.println();
	}

	public void printLine(long[] array) {
		print(array);
		writer.println();
	}

	public void printLine() {
		writer.println();
	}

	public void printLine(Object... objects) {
		print(objects);
		writer.println();
	}

	public void print(char i) {
		writer.print(i);
	}

	public void printLine(char i) {
		writer.println(i);
	}

	public void printLine(char[] array) {
		writer.println(array);
	}

	public void printFormat(String format, Object... objects) {
		writer.printf(format, objects);
	}

	public void close() {
		writer.close();
	}

	public void flush() {
		writer.flush();
	}

	public void print(long i) {
		writer.print(i);
	}

	public void printLine(long i) {
		writer.println(i);
	}

	public void print(int i) {
		writer.print(i);
	}

	public void printLine(int i) {
		writer.println(i);
	}
}

class IOUtils {

	public static int[] readIntArray(InputReader in, int size) {
		int[] array = new int[size];
		for (int i = 0; i < size; i++)
			array[i] = in.readInt();
		return array;
	}

	public static long[] readLongArray(InputReader in, int size) {
		long[] array = new long[size];
		for (int i = 0; i < size; i++)
			array[i] = in.readLong();
		return array;
	}

	public static double[] readDoubleArray(InputReader in, int size) {
		double[] array = new double[size];
		for (int i = 0; i < size; i++)
			array[i] = in.readDouble();
		return array;
	}

	public static String[] readStringArray(InputReader in, int size) {
		String[] array = new String[size];
		for (int i = 0; i < size; i++)
			array[i] = in.readString();
		return array;
	}

	public static char[] readCharArray(InputReader in, int size) {
		char[] array = new char[size];
		for (int i = 0; i < size; i++)
			array[i] = in.readCharacter();
		return array;
	}

	public static void readIntArrays(InputReader in, int[]... arrays) {
		for (int i = 0; i < arrays[0].length; i++) {
			for (int j = 0; j < arrays.length; j++)
				arrays[j][i] = in.readInt();
		}
	}

	public static void readLongArrays(InputReader in, long[]... arrays) {
		for (int i = 0; i < arrays[0].length; i++) {
			for (int j = 0; j < arrays.length; j++)
				arrays[j][i] = in.readLong();
		}
	}

	public static void readDoubleArrays(InputReader in, double[]... arrays) {
		for (int i = 0; i < arrays[0].length; i++) {
			for (int j = 0; j < arrays.length; j++)
				arrays[j][i] = in.readDouble();
		}
	}

	public static char[][] readTable(InputReader in, int rowCount,
			int columnCount) {
		char[][] table = new char[rowCount][];
		for (int i = 0; i < rowCount; i++)
			table[i] = readCharArray(in, columnCount);
		return table;
	}

	public static int[][] readIntTable(InputReader in, int rowCount,
			int columnCount) {
		int[][] table = new int[rowCount][];
		for (int i = 0; i < rowCount; i++)
			table[i] = readIntArray(in, columnCount);
		return table;
	}

	public static double[][] readDoubleTable(InputReader in, int rowCount,
			int columnCount) {
		double[][] table = new double[rowCount][];
		for (int i = 0; i < rowCount; i++)
			table[i] = readDoubleArray(in, columnCount);
		return table;
	}

	public static long[][] readLongTable(InputReader in, int rowCount,
			int columnCount) {
		long[][] table = new long[rowCount][];
		for (int i = 0; i < rowCount; i++)
			table[i] = readLongArray(in, columnCount);
		return table;
	}

	public static String[][] readStringTable(InputReader in, int rowCount,
			int columnCount) {
		String[][] table = new String[rowCount][];
		for (int i = 0; i < rowCount; i++)
			table[i] = readStringArray(in, columnCount);
		return table;
	}

	public static String readText(InputReader in) {
		StringBuilder result = new StringBuilder();
		while (true) {
			int character = in.read();
			if (character == '\r')
				continue;
			if (character == -1)
				break;
			result.append((char) character);
		}
		return result.toString();
	}

	public static void readStringArrays(InputReader in, String[]... arrays) {
		for (int i = 0; i < arrays[0].length; i++) {
			for (int j = 0; j < arrays.length; j++)
				arrays[j][i] = in.readString();
		}
	}

	public static void printTable(OutputWriter out, char[][] table) {
		for (char[] row : table)
			out.printLine(new String(row));
	}
}

class SumIntervalTree extends LongIntervalTree {
	public SumIntervalTree(int size) {
		super(size);
	}

	@Override
	protected long joinValue(long left, long right) {
		return left + right;
	}

	@Override
	protected long joinDelta(long was, long delta) {
		return was + delta;
	}

	@Override
	protected long accumulate(long value, long delta, int length) {
		return value + delta * length;
	}

	@Override
	protected long neutralValue() {
		return 0;
	}

	@Override
	protected long neutralDelta() {
		return 0;
	}
}

abstract class IntervalTree {
	protected int size;

	protected IntervalTree(int size) {
		this(size, true);
	}

	public IntervalTree(int size, boolean shouldInit) {
		this.size = size;
		int nodeCount = Math.max(1, Integer.highestOneBit(size) << 2);
		initData(size, nodeCount);
		if (shouldInit)
			init();
	}

	protected abstract void initData(int size, int nodeCount);

	protected abstract void initAfter(int root, int left, int right, int middle);

	protected abstract void initBefore(int root, int left, int right, int middle);

	protected abstract void initLeaf(int root, int index);

	protected abstract void updatePostProcess(int root, int left, int right,
			int from, int to, long delta, int middle);

	protected abstract void updatePreProcess(int root, int left, int right,
			int from, int to, long delta, int middle);

	protected abstract void updateFull(int root, int left, int right, int from,
			int to, long delta);

	protected abstract long queryPostProcess(int root, int left, int right,
			int from, int to, int middle, long leftResult, long rightResult);

	protected abstract void queryPreProcess(int root, int left, int right,
			int from, int to, int middle);

	protected abstract long queryFull(int root, int left, int right, int from,
			int to);

	protected abstract long emptySegmentResult();

	public void init() {
		if (size == 0)
			return;
		init(0, 0, size - 1);
	}

	private void init(int root, int left, int right) {
		if (left == right) {
			initLeaf(root, left);
		} else {
			int middle = (left + right) >> 1;
			initBefore(root, left, right, middle);
			init(2 * root + 1, left, middle);
			init(2 * root + 2, middle + 1, right);
			initAfter(root, left, right, middle);
		}
	}

	public void update(int from, int to, long delta) {
		update(0, 0, size - 1, from, to, delta);
	}

	protected void update(int root, int left, int right, int from, int to,
			long delta) {
		if (left > to || right < from)
			return;
		if (left >= from && right <= to) {
			updateFull(root, left, right, from, to, delta);
			return;
		}
		int middle = (left + right) >> 1;
		updatePreProcess(root, left, right, from, to, delta, middle);
		update(2 * root + 1, left, middle, from, to, delta);
		update(2 * root + 2, middle + 1, right, from, to, delta);
		updatePostProcess(root, left, right, from, to, delta, middle);
	}

	public long query(int from, int to) {
		return query(0, 0, size - 1, from, to);
	}

	protected long query(int root, int left, int right, int from, int to) {
		if (left > to || right < from)
			return emptySegmentResult();
		if (left >= from && right <= to)
			return queryFull(root, left, right, from, to);
		int middle = (left + right) >> 1;
		queryPreProcess(root, left, right, from, to, middle);
		long leftResult = query(2 * root + 1, left, middle, from, to);
		long rightResult = query(2 * root + 2, middle + 1, right, from, to);
		return queryPostProcess(root, left, right, from, to, middle,
				leftResult, rightResult);
	}
}

class TreapSet<K> implements NavigableSet<K> {
	protected static final Random rnd = new Random(239);

	protected final Node nullNode;
	protected final Comparator<? super K> comparator;
	protected Node root;
	private final K from;
	private final K to;
	private final boolean fromInclusive;
	private final boolean toInclusive;

	public TreapSet() {
		this((Comparator<? super K>) null);
	}

	public TreapSet(Comparator<? super K> comparator) {
		this(null, null, false, false, comparator, null, null);
	}

	public TreapSet(Iterable<? extends K> collection) {
		this(collection, null);
	}

	public TreapSet(Iterable<? extends K> collection,
			Comparator<? super K> comparator) {
		this(comparator);
		addAll(collection);
	}

	protected TreapSet(K from, K to, boolean fromInclusive,
			boolean toInclusive, Comparator<? super K> comparator, Node root,
			Node nullNode) {
		this.comparator = comparator;
		this.from = from;
		this.to = to;
		this.fromInclusive = fromInclusive;
		this.toInclusive = toInclusive;
		if (nullNode == null)
			nullNode = new NullNode();
		if (root == null)
			root = nullNode;
		this.root = root;
		this.nullNode = nullNode;
	}

	public boolean addAll(Iterable<? extends K> collection) {
		boolean result = false;
		for (K element : collection)
			result |= add(element);
		return result;
	}

	public K lower(K k) {
		Node target = root.lower(k);
		if (target == nullNode)
			return null;
		if (belongs(target.key))
			return target.key;
		return null;
	}

	private boolean belongs(K key) {
		int valueFrom = compare(from, key);
		int valueTo = compare(key, to);
		return (valueFrom < 0 || valueFrom == 0 && fromInclusive)
				&& (valueTo < 0 || valueTo == 0 && toInclusive);
	}

	public K floor(K k) {
		Node target = root.floor(k);
		if (target == nullNode)
			return null;
		if (belongs(target.key))
			return target.key;
		return null;
	}

	public K ceiling(K k) {
		Node target = root.ceil(k);
		if (target == nullNode)
			return null;
		if (belongs(target.key))
			return target.key;
		return null;
	}

	public K higher(K k) {
		Node target = root.higher(k);
		if (target == nullNode)
			return null;
		if (belongs(target.key))
			return target.key;
		return null;
	}

	public K pollFirst() {
		K first = first();
		if (first == null)
			throw new NoSuchElementException();
		root.erase(first);
		return first;
	}

	public K pollLast() {
		K last = last();
		if (last == null)
			throw new NoSuchElementException();
		root.erase(last);
		return last;
	}

	public int size() {
		if (from == null && to == null)
			return root.size;
		if (from == null) {
			Node to = toInclusive ? root.floor(this.to) : root.lower(this.to);
			if (to == nullNode)
				return 0;
			return root.indexOf(to) + 1;
		}
		if (to == null) {
			Node from = fromInclusive ? root.ceil(this.from) : root
					.higher(this.from);
			if (from == nullNode)
				return 0;
			return root.size - root.indexOf(from);
		}
		Node from = fromInclusive ? root.ceil(this.from) : root
				.higher(this.from);
		if (from == nullNode || !belongs(from.key))
			return 0;
		Node to = toInclusive ? root.floor(this.to) : root.lower(this.to);
		return root.indexOf(to) - root.indexOf(from) + 1;
	}

	public boolean isEmpty() {
		return size() == 0;
	}

	@SuppressWarnings({ "unchecked" })
	public boolean contains(Object o) {
		return belongs((K) o) && root.search((K) o) != nullNode;
	}

	public Iterator<K> iterator() {
		return new Iterator<K>() {
			private K current = first();

			public boolean hasNext() {
				return current != null;
			}

			public K next() {
				K result = current;
				current = higher(current);
				return result;
			}

			public void remove() {
				TreapSet.this.remove(current);
			}
		};
	}

	public Object[] toArray() {
		Object[] array = new Object[size()];
		int index = 0;
		for (K key : this)
			array[index++] = key;
		return array;
	}

	@SuppressWarnings({ "unchecked" })
	public <T> T[] toArray(T[] a) {
		if (a.length < size())
			throw new IllegalArgumentException();
		int index = 0;
		for (K key : this)
			a[index++] = (T) key;
		return a;
	}

	public boolean add(K k) {
		if (k == null)
			throw new NullPointerException();
		if (contains(k))
			return false;
		root = root.insert(createNode(k));
		return true;
	}

	protected Node createNode(K k) {
		return new Node(k, rnd.nextLong());
	}

	public boolean remove(Object o) {
		if (!contains(o))
			return false;
		// noinspection unchecked
		root = root.erase((K) o);
		return true;
	}

	public boolean containsAll(Collection<?> c) {
		for (Object o : c) {
			if (!contains(o))
				return false;
		}
		return true;
	}

	public boolean addAll(Collection<? extends K> c) {
		return addAll((Iterable<? extends K>) c);
	}

	public boolean retainAll(Collection<?> c) {
		List<K> toRemove = new ArrayList<K>();
		for (K key : this) {
			if (!c.contains(key))
				toRemove.add(key);
		}
		return removeAll(toRemove);
	}

	public boolean removeAll(Collection<?> c) {
		boolean result = false;
		for (Object o : c)
			result |= remove(o);
		return result;
	}

	public void clear() {
		retainAll(Collections.<Object> emptySet());
	}

	public NavigableSet<K> descendingSet() {
		throw new UnsupportedOperationException();
	}

	public Iterator<K> descendingIterator() {
		return new Iterator<K>() {
			private K current = last();

			public boolean hasNext() {
				return current != null;
			}

			public K next() {
				K result = current;
				current = lower(current);
				return result;
			}

			public void remove() {
				TreapSet.this.remove(current);
			}
		};
	}

	public NavigableSet<K> subSet(K fromElement, boolean fromInclusive,
			K toElement, boolean toInclusive) {
		return new TreapSet<K>(fromElement, toElement, fromInclusive,
				toInclusive, comparator, root, nullNode);
	}

	public NavigableSet<K> headSet(K toElement, boolean inclusive) {
		return subSet(null, false, toElement, inclusive);
	}

	public NavigableSet<K> tailSet(K fromElement, boolean inclusive) {
		return subSet(fromElement, inclusive, null, false);
	}

	public Comparator<? super K> comparator() {
		return comparator;
	}

	public SortedSet<K> subSet(K fromElement, K toElement) {
		return subSet(fromElement, true, toElement, false);
	}

	public SortedSet<K> headSet(K toElement) {
		return subSet(null, false, toElement, false);
	}

	public SortedSet<K> tailSet(K fromElement) {
		return tailSet(fromElement, true);
	}

	public K first() {
		if (isEmpty())
			return null;
		if (from == null)
			return root.first().key;
		if (fromInclusive)
			return ceiling(from);
		return higher(from);
	}

	public K last() {
		if (isEmpty())
			return null;
		if (to == null)
			return root.last().key;
		if (toInclusive)
			return floor(to);
		return lower(to);
	}

	public K get(int index) {
		if (index >= size() || index < 0)
			throw new IndexOutOfBoundsException(Integer.toString(index));
		if (from != null)
			index += headSet(from, !fromInclusive).size();
		return root.get(index);
	}

	protected int compare(K first, K second) {
		if (first == null || second == null)
			return -1;
		if (comparator != null)
			return comparator.compare(first, second);
		// noinspection unchecked
		return ((Comparable<? super K>) first).compareTo(second);
	}

	protected class Node {
		protected final K key;
		protected final long priority;
		protected Node left;
		protected Node right;
		protected int size;

		protected Node(K key, long priority) {
			this.key = key;
			this.priority = priority;
			left = nullNode;
			right = nullNode;
			size = 1;
		}

		@SuppressWarnings({ "unchecked" })
		protected Object[] split(K key) {
			if (compare(key, this.key) < 0) {
				Object[] result = left.split(key);
				left = (Node) result[1];
				result[1] = this;
				updateSize();
				return result;
			}
			Object[] result = right.split(key);
			right = (Node) result[0];
			result[0] = this;
			updateSize();
			return result;
		}

		protected void updateSize() {
			size = left.size + right.size + 1;
		}

		@SuppressWarnings({ "unchecked" })
		protected Node insert(Node node) {
			if (node.priority > priority) {
				Object[] result = split(node.key);
				node.left = (Node) result[0];
				node.right = (Node) result[1];
				node.updateSize();
				return node;
			}
			if (compare(node.key, this.key) < 0) {
				left = left.insert(node);
				updateSize();
				return this;
			}
			right = right.insert(node);
			updateSize();
			return this;
		}

		protected Node merge(Node left, Node right) {
			if (left == nullNode)
				return right;
			if (right == nullNode)
				return left;
			if (left.priority > right.priority) {
				left.right = left.right.merge(left.right, right);
				left.updateSize();
				return left;
			}
			right.left = right.left.merge(left, right.left);
			right.updateSize();
			return right;
		}

		protected Node erase(K key) {
			int value = compare(key, this.key);
			if (value == 0)
				return merge(left, right);
			if (value < 0) {
				left = left.erase(key);
				updateSize();
				return this;
			}
			right = right.erase(key);
			updateSize();
			return this;
		}

		protected Node lower(K key) {
			if (compare(key, this.key) <= 0)
				return left.lower(key);
			Node result = right.lower(key);
			if (result == nullNode)
				return this;
			return result;
		}

		protected Node floor(K key) {
			if (compare(key, this.key) < 0)
				return left.floor(key);
			Node result = right.floor(key);
			if (result == nullNode)
				return this;
			return result;
		}

		protected Node higher(K key) {
			if (compare(key, this.key) >= 0)
				return right.higher(key);
			Node result = left.higher(key);
			if (result == nullNode)
				return this;
			return result;
		}

		protected Node ceil(K key) {
			if (compare(key, this.key) > 0)
				return right.ceil(key);
			Node result = left.ceil(key);
			if (result == nullNode)
				return this;
			return result;
		}

		protected Node first() {
			if (left == nullNode)
				return this;
			return left.first();
		}

		protected Node last() {
			if (right == nullNode)
				return this;
			return right.last();
		}

		protected Node search(K key) {
			int value = compare(key, this.key);
			if (value == 0)
				return this;
			if (value < 0)
				return left.search(key);
			return right.search(key);
		}

		public int indexOf(Node node) {
			if (this == node)
				return left.size;
			if (compare(node.key, this.key) > 0)
				return left.size + 1 + right.indexOf(node);
			return left.indexOf(node);
		}

		public K get(int index) {
			if (index < left.size)
				return left.get(index);
			else if (index == left.size)
				return key;
			else
				return right.get(index - left.size - 1);
		}
	}

	private class NullNode extends Node {
		private Object[] splitResult = new Object[2];

		private NullNode() {
			super(null, Long.MIN_VALUE);
			left = this;
			right = this;
			size = 0;
		}

		@Override
		protected Object[] split(K key) {
			splitResult[0] = splitResult[1] = this;
			return splitResult;
		}

		@Override
		protected Node insert(Node node) {
			return node;
		}

		@Override
		protected Node erase(K key) {
			return this;
		}

		@Override
		protected Node lower(K key) {
			return this;
		}

		@Override
		protected Node floor(K key) {
			return this;
		}

		@Override
		protected Node higher(K key) {
			return this;
		}

		@Override
		protected Node ceil(K key) {
			return this;
		}

		@Override
		protected Node first() {
			throw new NoSuchElementException();
		}

		@Override
		protected Node last() {
			throw new NoSuchElementException();
		}

		@Override
		protected void updateSize() {
		}

		@Override
		protected Node search(K key) {
			return this;
		}

	}
}

abstract class LongIntervalTree extends IntervalTree {
	protected long[] value;
	protected long[] delta;

	protected LongIntervalTree(int size) {
		this(size, true);
	}

	public LongIntervalTree(int size, boolean shouldInit) {
		super(size, shouldInit);
	}

	@Override
	protected void initData(int size, int nodeCount) {
		value = new long[nodeCount];
		delta = new long[nodeCount];
	}

	protected abstract long joinValue(long left, long right);

	protected abstract long joinDelta(long was, long delta);

	protected abstract long accumulate(long value, long delta, int length);

	protected abstract long neutralValue();

	protected abstract long neutralDelta();

	protected long initValue(int index) {
		return neutralValue();
	}

	@Override
	protected void initAfter(int root, int left, int right, int middle) {
		value[root] = joinValue(value[2 * root + 1], value[2 * root + 2]);
		delta[root] = neutralDelta();
	}

	@Override
	protected void initBefore(int root, int left, int right, int middle) {
	}

	@Override
	protected void initLeaf(int root, int index) {
		value[root] = initValue(index);
		delta[root] = neutralDelta();
	}

	@Override
	protected void updatePostProcess(int root, int left, int right, int from,
			int to, long delta, int middle) {
		value[root] = joinValue(value[2 * root + 1], value[2 * root + 2]);
	}

	@Override
	protected void updatePreProcess(int root, int left, int right, int from,
			int to, long delta, int middle) {
		pushDown(root, left, middle, right);
	}

	protected void pushDown(int root, int left, int middle, int right) {
		value[2 * root + 1] = accumulate(value[2 * root + 1], delta[root],
				middle - left + 1);
		value[2 * root + 2] = accumulate(value[2 * root + 2], delta[root],
				right - middle);
		delta[2 * root + 1] = joinDelta(delta[2 * root + 1], delta[root]);
		delta[2 * root + 2] = joinDelta(delta[2 * root + 2], delta[root]);
		delta[root] = neutralDelta();
	}

	@Override
	protected void updateFull(int root, int left, int right, int from, int to,
			long delta) {
		value[root] = accumulate(value[root], delta, right - left + 1);
		this.delta[root] = joinDelta(this.delta[root], delta);
	}

	@Override
	protected long queryPostProcess(int root, int left, int right, int from,
			int to, int middle, long leftResult, long rightResult) {
		return joinValue(leftResult, rightResult);
	}

	@Override
	protected void queryPreProcess(int root, int left, int right, int from,
			int to, int middle) {
		pushDown(root, left, middle, right);
	}

	@Override
	protected long queryFull(int root, int left, int right, int from, int to) {
		return value[root];
	}

	@Override
	protected long emptySegmentResult() {
		return neutralValue();
	}
}

class IntPair implements Comparable<IntPair> {
	public final int first, second;

	public IntPair(int first, int second) {
		this.first = first;
		this.second = second;
	}

	@Override
	public String toString() {
		return "(" + first + "," + second + ")";
	}

	@Override
	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (o == null || getClass() != o.getClass())
			return false;

		IntPair intPair = (IntPair) o;

		return first == intPair.first && second == intPair.second;

	}

	@Override
	public int hashCode() {
		int result = first;
		result = 31 * result + second;
		return result;
	}

	public int compareTo(IntPair o) {
		if (first < o.first)
			return -1;
		if (first > o.first)
			return 1;
		if (second < o.second)
			return -1;
		if (second > o.second)
			return 1;
		return 0;
	}
}

class Matrix {
	public static long mod = Long.MAX_VALUE;
	public final long[][] data;
	public final int rowCount;
	public final int columnCount;

	public Matrix(int rowCount, int columnCount) {
		this.rowCount = rowCount;
		this.columnCount = columnCount;
		this.data = new long[rowCount][columnCount];
	}

	public Matrix(long[][] data) {
		this.rowCount = data.length;
		this.columnCount = data[0].length;
		this.data = data;
	}

	public static Matrix add(Matrix first, Matrix second) {
		Matrix result = new Matrix(first.rowCount, first.columnCount);
		for (int i = 0; i < result.rowCount; i++) {
			for (int j = 0; j < result.columnCount; j++) {
				result.data[i][j] = first.data[i][j] + second.data[i][j];
				if (result.data[i][j] >= mod)
					result.data[i][j] -= mod;
			}
		}
		return result;
	}

	public static Matrix multiply(Matrix first, Matrix second) {
		Matrix result = new Matrix(first.rowCount, second.columnCount);
		for (int i = 0; i < first.rowCount; i++) {
			for (int j = 0; j < second.rowCount; j++) {
				for (int k = 0; k < second.columnCount; k++)
					result.data[i][k] = (result.data[i][k] + first.data[i][j]
							* second.data[j][k])
							% mod;
			}
		}
		return result;
	}

	public static Matrix fastMultiply(Matrix first, Matrix second) {
		Matrix result = new Matrix(first.rowCount, second.columnCount);
		for (int i = 0; i < first.rowCount; i++) {
			for (int j = 0; j < second.rowCount; j++) {
				for (int k = 0; k < second.columnCount; k++)
					result.data[i][k] += first.data[i][j] * second.data[j][k];
			}
		}
		for (int i = 0; i < first.rowCount; i++) {
			for (int j = 0; j < second.columnCount; j++)
				result.data[i][j] %= mod;
		}
		return result;
	}

	public static Matrix identityMatrix(int size) {
		Matrix result = new Matrix(size, size);
		for (int i = 0; i < size; i++)
			result.data[i][i] = 1;
		return result;
	}

	public static long[] convert(long[][] matrix) {
		long[] result = new long[matrix.length * matrix.length];
		for (int i = 0; i < matrix.length; i++) {
			for (int j = 0; j < matrix.length; j++)
				result[i * matrix.length + j] = matrix[i][j];
		}
		return result;
	}

	public static long[] sumPowers(long[] matrix, long exponent, long mod,
			int side) {
		long[] result = new long[matrix.length];
		long[] power = new long[matrix.length];
		long[] temp = new long[matrix.length];
		long[] temp2 = new long[matrix.length];
		sumPowers(matrix, result, power, temp, temp2, exponent + 1, mod, side);
		return result;
	}

	private static void sumPowers(long[] matrix, long[] result, long[] power,
			long[] temp, long[] temp2, long exponent, long mod, int side) {
		if (exponent == 0) {
			for (int i = 0; i < matrix.length; i += side + 1)
				power[i] = 1 % mod;
			return;
		}
		if ((exponent & 1) == 0) {
			sumPowers(matrix, result, temp, power, temp2, exponent >> 1, mod,
					side);
			multiply(temp2, result, temp, mod, side);
			add(result, temp2, mod, side);
			multiply(power, temp, temp, mod, side);
		} else {
			sumPowers(matrix, result, temp, power, temp2, exponent - 1, mod,
					side);
			add(result, temp, mod, side);
			multiply(power, temp, matrix, mod, side);
		}
	}

	public static long[][] convert(long[] matrix, int side) {
		long[][] result = new long[side][side];
		for (int i = 0; i < side; i++) {
			for (int j = 0; j < side; j++)
				result[i][j] = matrix[i * side + j];
		}
		return result;
	}

	public static long[] power(long[] matrix, long exponent, long mod, int side) {
		long[] result = new long[matrix.length];
		long[] temp = new long[result.length];
		power(matrix, result, temp, exponent, mod, side);
		return result;
	}

	private static void power(long[] matrix, long[] result, long[] temp,
			long exponent, long mod, int side) {
		if (exponent == 0) {
			for (int i = 0; i < matrix.length; i += side + 1)
				result[i] = 1 % mod;
			return;
		}
		if ((exponent & 1) == 0) {
			power(matrix, temp, result, exponent >> 1, mod, side);
			multiply(result, temp, temp, mod, side);
		} else {
			power(matrix, temp, result, exponent - 1, mod, side);
			multiply(result, temp, matrix, mod, side);
		}
	}

	public static void multiply(long[] c, long[] a, long[] b, long mod, int side) {
		Arrays.fill(c, 0);
		for (int i = 0; i < side; i++) {
			for (int j = 0; j < side; j++) {
				for (int k = 0; k < side; k++) {
					c[i * side + k] += a[i * side + j] * b[j * side + k];
					if ((j & 3) == 3) {
						c[i * side + k] %= mod;
					}
				}
			}
		}
		for (int i = 0; i < c.length; i++)
			c[i] %= mod;
	}

	public static void add(long[] c, long[] a, long mod, int side) {
		for (int i = 0; i < side; i++) {
			for (int j = 0; j < side; j++) {
				c[i * side + j] += a[i * side + j];
				if (c[i * side + j] >= mod)
					c[i * side + j] -= mod;
			}
		}
	}

	public static long[] fastPower(long[] matrix, long exponent, long mod,
			int side) {
		long[] result = new long[matrix.length];
		long[] temp = new long[result.length];
		fastPower(matrix, result, temp, exponent, mod, side);
		return result;
	}

	private static void fastPower(long[] matrix, long[] result, long[] temp,
			long exponent, long mod, int side) {
		if (exponent == 0) {
			for (int i = 0; i < matrix.length; i += side + 1)
				result[i] = 1;
			return;
		}
		if ((exponent & 1) == 0) {
			fastPower(matrix, temp, result, exponent >> 1, mod, side);
			fastMultiply(result, temp, temp, mod, side);
		} else {
			power(matrix, temp, result, exponent - 1, mod, side);
			fastMultiply(result, temp, matrix, mod, side);
		}
	}

	public static void fastMultiply(long[] c, long[] a, long[] b, long mod,
			int side) {
		Arrays.fill(c, 0);
		for (int i = 0; i < side; i++) {
			for (int j = 0; j < side; j++) {
				for (int k = 0; k < side; k++)
					c[i * side + k] += a[i * side + j] * b[j * side + k];
			}
		}
		for (int i = 0; i < c.length; i++)
			c[i] %= mod;
	}

	public Matrix power(long exponent) {
		if (exponent == 0)
			return identityMatrix(rowCount);
		if (exponent == 1)
			return this;
		Matrix result = power(exponent >> 1);
		result = multiply(result, result);
		if ((exponent & 1) == 1)
			result = multiply(result, this);
		return result;
	}

	public Matrix fastPower(long exponent) {
		if (exponent == 0)
			return identityMatrix(rowCount);
		if (exponent == 1)
			return this;
		Matrix result = power(exponent >> 1);
		result = fastMultiply(result, result);
		if ((exponent & 1) == 1)
			result = fastMultiply(result, this);
		return result;
	}
}

class MiscUtils {
	public static final int[] DX4 = { 1, 0, -1, 0 };
	public static final int[] DY4 = { 0, -1, 0, 1 };
	public static final int[] DX8 = { 1, 1, 1, 0, -1, -1, -1, 0 };
	public static final int[] DY8 = { -1, 0, 1, 1, 1, 0, -1, -1 };
	public static final int[] DX_KNIGHT = { 2, 1, -1, -2, -2, -1, 1, 2 };
	public static final int[] DY_KNIGHT = { 1, 2, 2, 1, -1, -2, -2, -1 };

	private static final String[] ROMAN_TOKENS = { "M", "CM", "D", "CD", "C",
			"XC", "L", "XL", "X", "IX", "V", "IV", "I" };
	private static final int[] ROMAN_VALUES = { 1000, 900, 500, 400, 100, 90,
			50, 40, 10, 9, 5, 4, 1 };

	public static long josephProblem(long n, int k) {
		if (n == 1)
			return 0;
		if (k == 1)
			return n - 1;
		if (k > n)
			return (josephProblem(n - 1, k) + k) % n;
		long count = n / k;
		long result = josephProblem(n - count, k);
		result -= n % k;
		if (result < 0)
			result += n;
		else
			result += result / (k - 1);
		return result;
	}

	public static boolean isValidCell(int row, int column, int rowCount,
			int columnCount) {
		return row >= 0 && row < rowCount && column >= 0
				&& column < columnCount;
	}

	public static long maximalRectangleSum(long[][] array) {
		int n = array.length;
		int m = array[0].length;
		long[][] partialSums = new long[n + 1][m + 1];
		for (int i = 0; i < n; i++) {
			long rowSum = 0;
			for (int j = 0; j < m; j++) {
				rowSum += array[i][j];
				partialSums[i + 1][j + 1] = partialSums[i][j + 1] + rowSum;
			}
		}
		long result = Long.MIN_VALUE;
		for (int i = 0; i < m; i++) {
			for (int j = i; j < m; j++) {
				long minPartialSum = 0;
				for (int k = 1; k <= n; k++) {
					long current = partialSums[k][j + 1] - partialSums[k][i];
					result = Math.max(result, current - minPartialSum);
					minPartialSum = Math.min(minPartialSum, current);
				}
			}
		}
		return result;
	}

	public static int parseIP(String ip) {
		String[] components = ip.split("[.]");
		int result = 0;
		for (int i = 0; i < 4; i++)
			result += (1 << (24 - 8 * i)) * Integer.parseInt(components[i]);
		return result;
	}

	public static String buildIP(int mask) {
		StringBuilder result = new StringBuilder();
		for (int i = 0; i < 4; i++) {
			if (i != 0)
				result.append('.');
			result.append(mask >> (24 - 8 * i) & 255);
		}
		return result.toString();
	}

	public static <T> boolean equals(T first, T second) {
		return first == null && second == null || first != null
				&& first.equals(second);
	}

	public static boolean isVowel(char ch) {
		ch = Character.toUpperCase(ch);
		return ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U'
				|| ch == 'Y';
	}

	public static boolean isStrictVowel(char ch) {
		ch = Character.toUpperCase(ch);
		return ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U';
	}

	public static String convertToRoman(int number) {
		StringBuilder result = new StringBuilder();
		for (int i = 0; i < ROMAN_TOKENS.length; i++) {
			while (number >= ROMAN_VALUES[i]) {
				number -= ROMAN_VALUES[i];
				result.append(ROMAN_TOKENS[i]);
			}
		}
		return result.toString();
	}

	public static int convertFromRoman(String number) {
		int result = 0;
		for (int i = 0; i < ROMAN_TOKENS.length; i++) {
			while (number.startsWith(ROMAN_TOKENS[i])) {
				number = number.substring(ROMAN_TOKENS[i].length());
				result += ROMAN_VALUES[i];
			}
		}
		return result;
	}

	public static int distance(int x1, int y1, int x2, int y2) {
		int dx = x1 - x2;
		int dy = y1 - y2;
		return dx * dx + dy * dy;
	}

	public static <T extends Comparable<T>> T min(T first, T second) {
		if (first.compareTo(second) <= 0)
			return first;
		return second;
	}

	public static <T extends Comparable<T>> T max(T first, T second) {
		if (first.compareTo(second) <= 0)
			return second;
		return first;
	}

	public static void decreaseByOne(int[]... arrays) {
		for (int[] array : arrays) {
			for (int i = 0; i < array.length; i++)
				array[i]--;
		}
	}

	public static int[] getIntArray(String s) {
		String[] tokens = s.split(" ");
		int[] result = new int[tokens.length];
		for (int i = 0; i < result.length; i++)
			result[i] = Integer.parseInt(tokens[i]);
		return result;
	}
}

class Graph {
	public static final int REMOVED_BIT = 0;

	protected int vertexCount;
	protected int edgeCount;

	private int[] firstOutbound;
	private int[] firstInbound;

	private Edge[] edges;
	private int[] nextInbound;
	private int[] nextOutbound;
	private int[] from;
	private int[] to;
	private long[] weight;
	public long[] capacity;
	private int[] reverseEdge;
	private int[] flags;

	public Graph(int vertexCount) {
		this(vertexCount, vertexCount);
	}

	public Graph(int vertexCount, int edgeCapacity) {
		this.vertexCount = vertexCount;
		firstOutbound = new int[vertexCount];
		Arrays.fill(firstOutbound, -1);

		from = new int[edgeCapacity];
		to = new int[edgeCapacity];
		nextOutbound = new int[edgeCapacity];
		flags = new int[edgeCapacity];
	}

	public static Graph createGraph(int vertexCount, int[] from, int[] to) {
		Graph graph = new Graph(vertexCount, from.length);
		for (int i = 0; i < from.length; i++)
			graph.addSimpleEdge(from[i], to[i]);
		return graph;
	}

	public static Graph createWeightedGraph(int vertexCount, int[] from,
			int[] to, long[] weight) {
		Graph graph = new Graph(vertexCount, from.length);
		for (int i = 0; i < from.length; i++)
			graph.addWeightedEdge(from[i], to[i], weight[i]);
		return graph;
	}

	public static Graph createFlowGraph(int vertexCount, int[] from, int[] to,
			long[] capacity) {
		Graph graph = new Graph(vertexCount, from.length * 2);
		for (int i = 0; i < from.length; i++)
			graph.addFlowEdge(from[i], to[i], capacity[i]);
		return graph;
	}

	public static Graph createFlowWeightedGraph(int vertexCount, int[] from,
			int[] to, long[] weight, long[] capacity) {
		Graph graph = new Graph(vertexCount, from.length * 2);
		for (int i = 0; i < from.length; i++)
			graph.addFlowWeightedEdge(from[i], to[i], weight[i], capacity[i]);
		return graph;
	}

	public static Graph createTree(int[] parent) {
		Graph graph = new Graph(parent.length + 1, parent.length);
		for (int i = 0; i < parent.length; i++)
			graph.addSimpleEdge(parent[i], i + 1);
		return graph;
	}

	public int addEdge(int fromID, int toID, long weight, long capacity,
			int reverseEdge) {
		ensureEdgeCapacity(edgeCount + 1);
		if (firstOutbound[fromID] != -1)
			nextOutbound[edgeCount] = firstOutbound[fromID];
		else
			nextOutbound[edgeCount] = -1;
		firstOutbound[fromID] = edgeCount;
		if (firstInbound != null) {
			if (firstInbound[toID] != -1)
				nextInbound[edgeCount] = firstInbound[toID];
			else
				nextInbound[edgeCount] = -1;
			firstInbound[toID] = edgeCount;
		}
		this.from[edgeCount] = fromID;
		this.to[edgeCount] = toID;
		if (capacity != 0) {
			if (this.capacity == null)
				this.capacity = new long[from.length];
			this.capacity[edgeCount] = capacity;
		}
		if (weight != 0) {
			if (this.weight == null)
				this.weight = new long[from.length];
			this.weight[edgeCount] = weight;
		}
		if (reverseEdge != -1) {
			if (this.reverseEdge == null) {
				this.reverseEdge = new int[from.length];
				Arrays.fill(this.reverseEdge, 0, edgeCount, -1);
			}
			this.reverseEdge[edgeCount] = reverseEdge;
		}
		if (edges != null)
			edges[edgeCount] = createEdge(edgeCount);
		return edgeCount++;
	}

	protected final GraphEdge createEdge(int id) {
		return new GraphEdge(id);
	}

	public final int addFlowWeightedEdge(int from, int to, long weight,
			long capacity) {
		if (capacity == 0) {
			return addEdge(from, to, weight, 0, -1);
		} else {
			int lastEdgeCount = edgeCount;
			addEdge(to, from, -weight, 0, lastEdgeCount + entriesPerEdge());
			return addEdge(from, to, weight, capacity, lastEdgeCount);
		}
	}

	protected int entriesPerEdge() {
		return 1;
	}

	public final int addFlowEdge(int from, int to, long capacity) {
		return addFlowWeightedEdge(from, to, 0, capacity);
	}

	public final int addWeightedEdge(int from, int to, long weight) {
		return addFlowWeightedEdge(from, to, weight, 0);
	}

	public final int addSimpleEdge(int from, int to) {
		return addWeightedEdge(from, to, 0);
	}

	public final int vertexCount() {
		return vertexCount;
	}

	public final int edgeCount() {
		return edgeCount;
	}

	protected final int edgeCapacity() {
		return from.length;
	}

	public final Edge edge(int id) {
		initEdges();
		return edges[id];
	}

	public final int firstOutbound(int vertex) {
		int id = firstOutbound[vertex];
		while (id != -1 && isRemoved(id))
			id = nextOutbound[id];
		return id;
	}

	public final int nextOutbound(int id) {
		id = nextOutbound[id];
		while (id != -1 && isRemoved(id))
			id = nextOutbound[id];
		return id;
	}

	public final int firstInbound(int vertex) {
		initInbound();
		int id = firstInbound[vertex];
		while (id != -1 && isRemoved(id))
			id = nextInbound[id];
		return id;
	}

	public final int nextInbound(int id) {
		initInbound();
		id = nextInbound[id];
		while (id != -1 && isRemoved(id))
			id = nextInbound[id];
		return id;
	}

	public final int source(int id) {
		return from[id];
	}

	public final int destination(int id) {
		return to[id];
	}

	public final long weight(int id) {
		if (weight == null)
			return 0;
		return weight[id];
	}

	public final long capacity(int id) {
		if (capacity == null)
			return 0;
		return capacity[id];
	}

	public final long flow(int id) {
		if (reverseEdge == null)
			return 0;
		return capacity[reverseEdge[id]];
	}

	public final void pushFlow(int id, long flow) {
		if (flow == 0)
			return;
		if (flow > 0) {
			if (capacity(id) < flow)
				throw new IllegalArgumentException("Not enough capacity");
		} else {
			if (flow(id) < -flow)
				throw new IllegalArgumentException("Not enough capacity");
		}
		capacity[id] -= flow;
		capacity[reverseEdge[id]] += flow;
	}

	public int transposed(int id) {
		return -1;
	}

	public final int reverse(int id) {
		if (reverseEdge == null)
			return -1;
		return reverseEdge[id];
	}

	public final void addVertices(int count) {
		ensureVertexCapacity(vertexCount + count);
		Arrays.fill(firstOutbound, vertexCount, vertexCount + count, -1);
		if (firstInbound != null)
			Arrays.fill(firstInbound, vertexCount, vertexCount + count, -1);
		vertexCount += count;
	}

	protected final void initEdges() {
		if (edges == null) {
			edges = new Edge[from.length];
			for (int i = 0; i < edgeCount; i++)
				edges[i] = createEdge(i);
		}
	}

	public final void removeVertex(int vertex) {
		int id = firstOutbound[vertex];
		while (id != -1) {
			removeEdge(id);
			id = nextOutbound[id];
		}
		initInbound();
		id = firstInbound[vertex];
		while (id != -1) {
			removeEdge(id);
			id = nextInbound[id];
		}
	}

	private void initInbound() {
		if (firstInbound == null) {
			firstInbound = new int[firstOutbound.length];
			Arrays.fill(firstInbound, 0, vertexCount, -1);
			nextInbound = new int[from.length];
			for (int i = 0; i < edgeCount; i++) {
				nextInbound[i] = firstInbound[to[i]];
				firstInbound[to[i]] = i;
			}
		}
	}

	public final boolean flag(int id, int bit) {
		return (flags[id] >> bit & 1) != 0;
	}

	public final void setFlag(int id, int bit) {
		flags[id] |= 1 << bit;
	}

	public final void removeFlag(int id, int bit) {
		flags[id] &= -1 - (1 << bit);
	}

	public final void removeEdge(int id) {
		setFlag(id, REMOVED_BIT);
	}

	public final void restoreEdge(int id) {
		removeFlag(id, REMOVED_BIT);
	}

	public final boolean isRemoved(int id) {
		return flag(id, REMOVED_BIT);
	}

	public final Iterable<Edge> outbound(final int id) {
		initEdges();
		return new Iterable<Edge>() {
			public Iterator<Edge> iterator() {
				return new EdgeIterator(id, firstOutbound, nextOutbound);
			}
		};
	}

	public final Iterable<Edge> inbound(final int id) {
		initEdges();
		initInbound();
		return new Iterable<Edge>() {
			public Iterator<Edge> iterator() {
				return new EdgeIterator(id, firstInbound, nextInbound);
			}
		};
	}

	protected void ensureEdgeCapacity(int size) {
		if (from.length < size) {
			int newSize = Math.max(size, 2 * from.length);
			if (edges != null)
				edges = resize(edges, newSize);
			from = resize(from, newSize);
			to = resize(to, newSize);
			nextOutbound = resize(nextOutbound, newSize);
			if (nextInbound != null)
				nextInbound = resize(nextInbound, newSize);
			if (weight != null)
				weight = resize(weight, newSize);
			if (capacity != null)
				capacity = resize(capacity, newSize);
			if (reverseEdge != null)
				reverseEdge = resize(reverseEdge, newSize);
			flags = resize(flags, newSize);
		}
	}

	private void ensureVertexCapacity(int size) {
		if (firstOutbound.length < size) {
			int newSize = Math.max(size, 2 * from.length);
			firstOutbound = resize(firstOutbound, newSize);
			if (firstInbound != null)
				firstInbound = resize(firstInbound, newSize);
		}
	}

	protected final int[] resize(int[] array, int size) {
		int[] newArray = new int[size];
		System.arraycopy(array, 0, newArray, 0, array.length);
		return newArray;
	}

	private long[] resize(long[] array, int size) {
		long[] newArray = new long[size];
		System.arraycopy(array, 0, newArray, 0, array.length);
		return newArray;
	}

	private Edge[] resize(Edge[] array, int size) {
		Edge[] newArray = new Edge[size];
		System.arraycopy(array, 0, newArray, 0, array.length);
		return newArray;
	}

	public final boolean isSparse() {
		return vertexCount == 0 || edgeCount * 20 / vertexCount <= vertexCount;
	}

	protected class GraphEdge implements Edge {
		protected int id;

		protected GraphEdge(int id) {
			this.id = id;
		}

		public int getSource() {
			return source(id);
		}

		public int getDestination() {
			return destination(id);
		}

		public long getWeight() {
			return weight(id);
		}

		public long getCapacity() {
			return capacity(id);
		}

		public long getFlow() {
			return flow(id);
		}

		public void pushFlow(long flow) {
			Graph.this.pushFlow(id, flow);
		}

		public boolean getFlag(int bit) {
			return flag(id, bit);
		}

		public void setFlag(int bit) {
			Graph.this.setFlag(id, bit);
		}

		public void removeFlag(int bit) {
			Graph.this.removeFlag(id, bit);
		}

		public int getTransposedID() {
			return transposed(id);
		}

		public Edge getTransposedEdge() {
			int reverseID = getTransposedID();
			if (reverseID == -1)
				return null;
			initEdges();
			return edge(reverseID);
		}

		public int getReverseID() {
			return reverse(id);
		}

		public Edge getReverseEdge() {
			int reverseID = getReverseID();
			if (reverseID == -1)
				return null;
			initEdges();
			return edge(reverseID);
		}

		public int getID() {
			return id;
		}

		public void remove() {
			removeEdge(id);
		}

		public void restore() {
			restoreEdge(id);
		}
	}

	public class EdgeIterator implements Iterator<Edge> {
		private int edgeID;
		private final int[] next;
		private int lastID = -1;

		public EdgeIterator(int id, int[] first, int[] next) {
			this.next = next;
			edgeID = nextEdge(first[id]);
		}

		private int nextEdge(int id) {
			while (id != -1 && isRemoved(id))
				id = next[id];
			return id;
		}

		public boolean hasNext() {
			return edgeID != -1;
		}

		public Edge next() {
			if (edgeID == -1)
				throw new NoSuchElementException();
			lastID = edgeID;
			edgeID = nextEdge(next[lastID]);
			return edges[lastID];
		}

		public void remove() {
			if (lastID == -1)
				throw new IllegalStateException();
			removeEdge(lastID);
			lastID = -1;
		}
	}

}

class MaxFlow {
	private final Graph graph;
	private int source;
	private int destination;
	private int[] queue;
	private int[] distance;
	private int[] nextEdge;

	private MaxFlow(Graph graph, int source, int destination) {
		this.graph = graph;
		this.source = source;
		this.destination = destination;
		int vertexCount = graph.vertexCount();
		queue = new int[vertexCount];
		distance = new int[vertexCount];
		nextEdge = new int[vertexCount];
	}

	public static long dinic(Graph graph, int source, int destination) {
		return new MaxFlow(graph, source, destination).dinic();
	}

	private long dinic() {
		long totalFlow = 0;
		while (true) {
			edgeDistances();
			if (distance[destination] == -1)
				break;
			Arrays.fill(nextEdge, -2);
			totalFlow += dinicImpl(source, Long.MAX_VALUE);
		}
		return totalFlow;
	}

	private void edgeDistances() {
		Arrays.fill(distance, -1);
		distance[source] = 0;
		int size = 1;
		queue[0] = source;
		for (int i = 0; i < size; i++) {
			int current = queue[i];
			int id = graph.firstOutbound(current);
			while (id != -1) {
				if (graph.capacity(id) != 0) {
					int next = graph.destination(id);
					if (distance[next] == -1) {
						distance[next] = distance[current] + 1;
						queue[size++] = next;
					}
				}
				id = graph.nextOutbound(id);
			}
		}
	}

	private long dinicImpl(int source, long flow) {
		if (source == destination)
			return flow;
		if (flow == 0 || distance[source] == distance[destination])
			return 0;
		int id = nextEdge[source];
		if (id == -2)
			nextEdge[source] = id = graph.firstOutbound(source);
		long totalPushed = 0;
		while (id != -1) {
			int nextDestinationID = graph.destination(id);
			if (graph.capacity(id) != 0
					&& distance[nextDestinationID] == distance[source] + 1) {
				long pushed = dinicImpl(nextDestinationID,
						Math.min(flow, graph.capacity(id)));
				if (pushed != 0) {
					graph.pushFlow(id, pushed);
					flow -= pushed;
					totalPushed += pushed;
					if (flow == 0)
						return totalPushed;
				}
			}
			nextEdge[source] = id = graph.nextOutbound(id);
		}
		return totalPushed;
	}
}

interface Edge {
	public int getSource();

	public int getDestination();

	public long getWeight();

	public long getCapacity();

	public long getFlow();

	public void pushFlow(long flow);

	public boolean getFlag(int bit);

	public void setFlag(int bit);

	public void removeFlag(int bit);

	public int getTransposedID();

	public Edge getTransposedEdge();

	public int getReverseID();

	public Edge getReverseEdge();

	public int getID();

	public void remove();

	public void restore();
}

class Point {
	public static final Point ORIGIN = new Point(0, 0);
	public final double x;
	public final double y;

	@Override
	public String toString() {
		return "(" + x + ", " + y + ")";
	}

	public Point(double x, double y) {
		this.x = x;
		this.y = y;
	}

	public Line line(Point other) {
		if (equals(other))
			return null;
		double a = other.y - y;
		double b = x - other.x;
		double c = -a * x - b * y;
		return new Line(a, b, c);
	}

	@Override
	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (o == null || getClass() != o.getClass())
			return false;

		Point point = (Point) o;

		return Math.abs(x - point.x) <= GeometryUtils.epsilon
				&& Math.abs(y - point.y) <= GeometryUtils.epsilon;
	}

	@Override
	public int hashCode() {
		int result;
		long temp;
		temp = x != +0.0d ? Double.doubleToLongBits(x) : 0L;
		result = (int) (temp ^ (temp >>> 32));
		temp = y != +0.0d ? Double.doubleToLongBits(y) : 0L;
		result = 31 * result + (int) (temp ^ (temp >>> 32));
		return result;
	}

	public double distance(Point other) {
		return GeometryUtils.fastHypot(x - other.x, y - other.y);
	}

	public double distance(Line line) {
		return Math.abs(line.a * x + line.b * y + line.c);
	}

	public double value() {
		return GeometryUtils.fastHypot(x, y);
	}

	public double angle() {
		return Math.atan2(y, x);
	}

	public static Point readPoint(InputReader in) {
		double x = in.readDouble();
		double y = in.readDouble();
		return new Point(x, y);
	}

	public Point rotate(double angle) {
		double nx = x * Math.cos(angle) - y * Math.sin(angle);
		double ny = y * Math.cos(angle) + x * Math.sin(angle);
		return new Point(nx, ny);
	}
}

class Line {
	public final double a;
	public final double b;
	public final double c;

	public Line(Point p, double angle) {
		a = Math.sin(angle);
		b = -Math.cos(angle);
		c = -p.x * a - p.y * b;
	}

	public Line(double a, double b, double c) {
		double h = GeometryUtils.fastHypot(a, b);
		this.a = a / h;
		this.b = b / h;
		this.c = c / h;
	}

	public Point intersect(Line other) {
		if (parallel(other))
			return null;
		double determinant = b * other.a - a * other.b;
		double x = (c * other.b - b * other.c) / determinant;
		double y = (a * other.c - c * other.a) / determinant;
		return new Point(x, y);
	}

	public boolean parallel(Line other) {
		return Math.abs(a * other.b - b * other.a) < GeometryUtils.epsilon;
	}

	public boolean contains(Point point) {
		return Math.abs(value(point)) < GeometryUtils.epsilon;
	}

	public Line perpendicular(Point point) {
		return new Line(-b, a, b * point.x - a * point.y);
	}

	public double value(Point point) {
		return a * point.x + b * point.y + c;
	}

	public double distance(Point center) {
		return Math.abs(value(center));
	}

	@Override
	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (o == null || getClass() != o.getClass())
			return false;

		Line line = (Line) o;

		if (!parallel(line))
			return false;
		if (Math.abs(a * line.c - c * line.a) > GeometryUtils.epsilon
				|| Math.abs(b * line.c - c * line.b) > GeometryUtils.epsilon)
			return false;

		return true;
	}
}

class GeometryUtils {
	public static double epsilon = 1e-8;

	public static double fastHypot(double... x) {
		if (x.length == 0)
			return 0;
		else if (x.length == 1)
			return Math.abs(x[0]);
		else {
			double sumSquares = 0;
			for (double value : x)
				sumSquares += value * value;
			return Math.sqrt(sumSquares);
		}
	}

	public static double fastHypot(double x, double y) {
		return Math.sqrt(x * x + y * y);
	}

	public static double fastHypot(double[] x, double[] y) {
		if (x.length == 0)
			return 0;
		else if (x.length == 1)
			return Math.abs(x[0] - y[0]);
		else {
			double sumSquares = 0;
			for (int i = 0; i < x.length; i++) {
				double diff = x[i] - y[i];
				sumSquares += diff * diff;
			}
			return Math.sqrt(sumSquares);
		}
	}

	public static double fastHypot(int[] x, int[] y) {
		if (x.length == 0)
			return 0;
		else if (x.length == 1)
			return Math.abs(x[0] - y[0]);
		else {
			double sumSquares = 0;
			for (int i = 0; i < x.length; i++) {
				double diff = x[i] - y[i];
				sumSquares += diff * diff;
			}
			return Math.sqrt(sumSquares);
		}
	}

	public static double missileTrajectoryLength(double v, double angle,
			double g) {
		return (v * v * Math.sin(2 * angle)) / g;
	}

	public static double sphereVolume(double radius) {
		return 4 * Math.PI * radius * radius * radius / 3;
	}

	public static double triangleSquare(double first, double second,
			double third) {
		double p = (first + second + third) / 2;
		return Math.sqrt(p * (p - first) * (p - second) * (p - third));
	}

	public static double canonicalAngle(double angle) {
		while (angle > Math.PI)
			angle -= 2 * Math.PI;
		while (angle < -Math.PI)
			angle += 2 * Math.PI;
		return angle;
	}

	public static double positiveAngle(double angle) {
		while (angle > 2 * Math.PI - GeometryUtils.epsilon)
			angle -= 2 * Math.PI;
		while (angle < -GeometryUtils.epsilon)
			angle += 2 * Math.PI;
		return angle;
	}
}