Emuskald is a well-known illusionist. One of his trademark tricks involves a set of magical boxes. The essence of the trick is in packing the boxes inside other boxes.

From the top view each magical box looks like a square with side length equal to 2k (k is an integer, k ≥ 0) units. A magical box v can be put inside a magical box u, if side length of v is strictly less than the side length of u. In particular, Emuskald can put 4 boxes of side length 2k - 1 into one box of side length 2k, or as in the following figure:

<image>

Emuskald is about to go on tour performing around the world, and needs to pack his magical boxes for the trip. He has decided that the best way to pack them would be inside another magical box, but magical boxes are quite expensive to make. Help him find the smallest magical box that can fit all his boxes.

Input

The first line of input contains an integer n (1 ≤ n ≤ 105), the number of different sizes of boxes Emuskald has. Each of following n lines contains two integers ki and ai (0 ≤ ki ≤ 109, 1 ≤ ai ≤ 109), which means that Emuskald has ai boxes with side length 2ki. It is guaranteed that all of ki are distinct.

Output

Output a single integer p, such that the smallest magical box that can contain all of Emuskald’s boxes has side length 2p.

Examples

Input

2
0 3
1 5


Output

3


Input

1
0 4


Output

1


Input

2
1 10
2 2


Output

3

Note

Picture explanation. If we have 3 boxes with side length 2 and 5 boxes with side length 1, then we can put all these boxes inside a box with side length 4, for example, as shown in the picture.

In the second test case, we can put all four small boxes into a box with side length 2.
import java.io.*;
import java.util.*;
 
 
 
public class Main {
	
	static InputReader in = new InputReader(System.in);
	static PrintWriter out = new PrintWriter(System.out);
	
	static int oo = (int)1e9;
//	static long oo = (long)1e15;
	static int mod = 1_000_000_007;
	
	static int[] di = {1, 0, 0, -1};
	static int[] dj = {0, -1, 1, 0};
	
	static long M = (long)1e17;
	static double EPS = 1e-13;
	
	
	
	public static void main(String[] args) throws IOException {

		int n = in.nextInt();
		Box[] a = new Box[n];
		for(int i = 0; i < n; ++i) {
			a[i] = new Box(in.nextLong(), in.nextLong());
		}
		Arrays.parallelSort(a, (x, y) -> Long.compare(x.k, y.k));
		long k = a[0].k;
		long cnt = a[0].cnt;
		for(int i = 1; i < n; ++i) {
			while(k < a[i].k && cnt > 1) {
				cnt = cnt / 4 + (cnt % 4 > 0 ? 1 : 0);
				k++;
			}
			k = a[i].k;
			cnt = Math.max(cnt, a[i].cnt);
		}
		if(cnt == 1)
			System.out.println(k+1);
		else {
			while(cnt > 1) {
				cnt = cnt / 4 + (cnt % 4 > 0 ? 1 : 0);
				k++;
			}
			System.out.println(k);
		}
		
		out.close();
	}
	
	static class Box {
		long k;
		long cnt;
		public Box(long k, long cnt) {
			super();
			this.k = k;
			this.cnt = cnt;
		}
	}
	
	static int find(int[] g, int x) {
		return g[x] = g[x] == x ? x : find(g, g[x]);
	}
	
	static void union(int[] g, int[] size, int x, int y) {
		x = find(g, x); y = find(g, y);
		if(x == y)
			return;
		if(size[x] < size[y]) {
			g[x] = y;
			size[y] += size[x];
		}
		else {
			g[y] = x;
			size[x] += size[y];
		}
	}
	
	static class Segment {
		Segment left, right;
		int size, val;
		long lazy;
		
		public Segment(int[] a, int l, int r) {
			super();
			if(l == r) {
				val = a[l];
				size = 1;
				return;
			}
			int mid = (l + r) / 2;
			left = new Segment(a, l, mid);
			right = new Segment(a, mid+1, r);
			size = left.size + right.size;
		}
		
		boolean covered(int ll, int rr, int l, int r) {
			return ll <= l && rr >= r;
		}
		
		boolean noIntersection(int ll, int rr, int l, int r) {
			return ll > r || rr < l;
		}
		
//		void lazyPropagation(int l, int r) {
//			if(lazy != 0) {
//				set(lazy, l, r); 
//				if(left != null) {
//					left.lazy += lazy;
//					right.lazy += lazy;
//				}
//				lazy = 0;
//			}
//		}
//		
//		void set(long delta, int l, int r) {
//			int sz = r - l + 1;
//			sum += delta * sz; 
//		}
		
//		long query(int ll, int rr, int l, int r) {
//			lazyPropagation(l, r);
//			if(noIntersection(ll, rr, l, r))
//				return 0;
//			if(covered(ll, rr, l, r))
//				return sum;
//			int mid = (l + r) / 2;
//			long leftSum = left.query(ll, rr, l, mid);
//			long rightSum = right.query(ll, rr, mid+1, r);
//			return leftSum + rightSum;
//		}
		
		int query(int k, int l, int r) {
			Segment trace = this;
			while(l < r) {
				int mid = (l + r) / 2;
				if(trace.left.size > k) {
					trace = trace.left;
					r = mid;
				}
				else {
					k -= trace.left.size;
					trace = trace.right;
					l = mid + 1;
				}
			}
			return l;
		}
		
		void update(int ll, int rr, int l, int r) {
			if(noIntersection(ll, rr, l, r))
				return;
			if(covered(ll, rr, l, r)) {
				size = 0;
				return;
			}
			int mid = (l + r) / 2;
			left.update(ll, rr, l, mid);
			right.update(ll, rr, mid+1, r);
			size = left.size + right.size;
		}
	}
	
	static long pow(long a, long n, long mod) {
		if(n == 0)
			return 1;
		if(n % 2 == 1)
			return a * pow(a, n-1, mod) % mod;
		long x = pow(a, n / 2, mod);
		return x * x % mod;
	}
	
	
	static int[] getPi(char[] a) {
		int m = a.length;
		int j = 0;
		int[] pi = new int[m];
		for(int i = 1; i < m; ++i) {
			while(j > 0 && a[i] != a[j])
				j = pi[j-1];
			if(a[i] == a[j]) {
				pi[i] = j + 1;
				j++;
			}
		}
		return pi;
	}
	
	static long lcm(long a, long b) {
		return a * b / gcd(a, b);
	}
	
	static boolean nextPermutation(int[] a) {
		for(int i = a.length - 2; i >= 0; --i) {
			if(a[i] < a[i+1]) {
				for(int j = a.length - 1; ; --j) {
					if(a[i] < a[j]) {
						int t = a[i];
						a[i] = a[j];
						a[j] = t;
						for(i++, j = a.length - 1; i < j; ++i, --j) {
							t = a[i];
							a[i] = a[j];
							a[j] = t;
						}
						return true;
					}
				}
			}
		}
		return false;
	}
	
	static void shuffle(Object[] a) {
		Random r = new Random();
		for(int i = a.length - 1; i > 0; --i) {
			int si = r.nextInt(i);
			Object t = a[si];
			a[si] = a[i];
			a[i] = t;
		}
	}
	
	static void shuffle(int[] a) {
		Random r = new Random();
		for(int i = a.length - 1; i > 0; --i) {
			int si = r.nextInt(i);
			int t = a[si];
			a[si] = a[i];
			a[i] = t;
		}
	}
	
	static void shuffle(long[] a) {
		Random r = new Random();
		for(int i = a.length - 1; i > 0; --i) {
			int si = r.nextInt(i);
			long t = a[si];
			a[si] = a[i];
			a[i] = t;
		}
	}
	
	static int lower_bound(int[] a, int n, int k) {
		int s = 0;
		int e = n;
		int m;
		while (e - s > 0) {
			m = (s + e) / 2;
			if (a[m] < k)
				s = m + 1;
			else
				e = m;
		}
		return e;
	}
	static int lower_bound(long[] a, int n, long k) {
		int s = 0;
		int e = n;
		int m;
		while (e - s > 0) {
			m = (s + e) / 2;
			if (a[m] < k)
				s = m + 1;
			else
				e = m;
		}
		return e;
	}
	
	static int gcd(int a, int b) {
		return b == 0 ? a : gcd(b, a % b);
	}
	static long gcd(long a, long b) {
		return b == 0 ? a : gcd(b, a % b);
	}
	
	static class Pair implements Comparable<Pair> {
		int first, second;
 
		public Pair(int first, int second) {
			super();
			this.first = first;
			this.second = second;
		}
 
		@Override
		public int compareTo(Pair o) {
			return this.first != o.first ? this.first - o.first : this.second - o.second;
		}
		
//		@Override
//		public int compareTo(Pair o) {
//			return this.first != o.first ? o.first - this.first : o.second - this.second;
//		}
 
		@Override
		public int hashCode() {
			final int prime = 31;
			int result = 1;
			result = prime * result + first;
			result = prime * result + second;
			return result;
		}
 
		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (obj == null)
				return false;
			if (getClass() != obj.getClass())
				return false;
			Pair other = (Pair) obj;
			if (first != other.first)
				return false;
			if (second != other.second)
				return false;
			return true;
		}
	}
}
 
 
 
class InputReader {
 
	private final InputStream stream;
	private final byte[] buf = new byte[8192];
	private int curChar, snumChars;
 
	public InputReader(InputStream st) {
		this.stream = st;
	}
 
	public int read() {
		if (snumChars == -1)
			throw new InputMismatchException();
		if (curChar >= snumChars) {
			curChar = 0;
			try {
				snumChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (snumChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}
 
	public int nextInt() {
		int c = read();
		while (isSpaceChar(c)) {
			c = read();
		}
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}
 
	public long nextLong() {
		int c = read();
		while (isSpaceChar(c)) {
			c = read();
		}
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		long res = 0;
		do {
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}
 
	public int[] nextIntArray(int n) {
		int a[] = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = nextInt();
		}
		return a;
	}
 
	public String readString() {
		int c = read();
		while (isSpaceChar(c)) {
			c = read();
		}
		StringBuilder res = new StringBuilder();
		do {
			res.appendCodePoint(c);
			c = read();
		} while (!isSpaceChar(c));
		return res.toString();
	}
 
	public String nextLine() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		StringBuilder res = new StringBuilder();
		do {
			res.appendCodePoint(c);
			c = read();
		} while (!isEndOfLine(c));
		return res.toString();
	}
 
	public boolean isSpaceChar(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}
 
	private boolean isEndOfLine(int c) {
		return c == '\n' || c == '\r' || c == -1;
	}
 
}