Andrewid the Android is a galaxy-famous detective. In his free time he likes to think about strings containing zeros and ones.

Once he thought about a string of length n consisting of zeroes and ones. Consider the following operation: we choose any two adjacent positions in the string, and if one them contains 0, and the other contains 1, then we are allowed to remove these two digits from the string, obtaining a string of length n - 2 as a result.

Now Andreid thinks about what is the minimum length of the string that can remain after applying the described operation several times (possibly, zero)? Help him to calculate this number.

Input

First line of the input contains a single integer n (1 ≤ n ≤ 2·105), the length of the string that Andreid has.

The second line contains the string of length n consisting only from zeros and ones.

Output

Output the minimum length of the string that may remain after applying the described operations several times.

Examples

Input

4
1100


Output

0


Input

5
01010


Output

1


Input

8
11101111


Output

6

Note

In the first sample test it is possible to change the string like the following: <image>.

In the second sample test it is possible to change the string like the following: <image>.

In the third sample test it is possible to change the string like the following: <image>.
import java.io.*;
import java.util.*;

public class Main {
    private final static InputReader ir = new InputReader(System.in);
    private final static OutputWriter ow = new OutputWriter(System.out);
    private final static int INF = Integer.MAX_VALUE;
    private final static int NINF = Integer.MIN_VALUE;
    private final static double PI = Math.PI;

    public static void main(String[] args) throws IOException {
        try {
            task();
        } finally {
            boolean exc = false;
            try {
                ir.close();
            } catch (IOException e) {
                e.printStackTrace();
                exc = true;
            }
            try {
                ow.close();
            } catch (IOException e) {
                e.printStackTrace();
                exc = true;
            }
            if (exc) System.exit(1);
        }
    }

    private static void task() throws IOException {
        int n = ir.nextInt();
        int cnto = 0, cntz = 0;
        for (int i = 0; i < n; ++i) {
            int c = ir.nextChar();
            if (c == '0') ++cntz;
            else ++cnto;
        }
        ow.print(n - 2 * min(cnto, cntz));
    }

    private static int max(int... objects) {
        if (objects.length == 0)
            throw new IllegalArgumentException("objects.length == 0");
        int max = objects[0];
        for (int i = 1; i < objects.length; ++i) {
            if (max < objects[i])
                max = objects[i];
        }
        return max;
    }

    private static int min(int... objects) {
        if (objects.length == 0)
            throw new IllegalArgumentException("objects.length == 0");
        int min = objects[0];
        for (int i = 1; i < objects.length; ++i) {
            if (min > objects[i])
                min = objects[i];
        }
        return min;
    }

    private static long pow(int x, int n) {
        if (x == 0) return 0;
        if (x == 1 || n == 0) return 1;
        if (x == 2) return x << (n - 1);
        if (n == 1) return x;
        long t = pow(x, n / 2);
        if (n % 2 == 0) return t * t;
        else return t * t * x;
    }

    private static double pow(double x, int n) {
        if (x == 0.0) return 0;
        if (x == 1.0 || n == 0) return 1;
        if (n == 1) return x;
        double t = pow(x, n / 2);
        if (n % 2 == 0) return t * t;
        else return t * t * x;
    }

    private static int abs(int a) {
        return (a >= 0 ? a : -a);
    }
}

class Pair<T, P> {
    T f;
    P s;
    Pair(T f, P s) {
        this.f = f;
        this.s = s;
    }
}

class Triple<T, P, V> {
    T f;
    P s;
    V t;
    Triple(T f, P s, V t) {
        this.f = f;
        this.s = s;
        this.t = t;
    }
}

class InputReader implements AutoCloseable {
    private final InputStream in;
    private int capacity;
    private byte[] buffer;
    private int len = 0;
    private int cur = 0;

    public InputReader(InputStream stream) {
        this(stream, 100_000);
    }

    public InputReader(InputStream stream, int capacity) {
        this.in = stream;
        this.capacity = capacity;
        buffer = new byte[capacity];
    }

    private boolean update() {
        if (cur >= len) {
            try {
                cur = 0;
                len = in.read(buffer, 0, capacity);
                if (len <= 0)
                    return false;
            } catch (IOException e) {
                throw new InputMismatchException();
            }
        }
        return true;
    }

    private int read() {
        if (update())
            return buffer[cur++];
        else return -1;
    }

    public boolean isEmpty() {
        return !update();
    }

    private boolean isSpace(int c) {
        return c == '\n' || c == '\t' || c == '\r' || c == ' ';
    }

    private boolean isEscape(int c) {
        return c == '\n' || c == '\t' || c == '\r' || c == -1;
    }

    private int readSkipSpace() {
        int c;
        do {
            c = read();
        } while (isSpace(c));
        return c;
    }

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

    public int[] getAllInts() {
        List<Integer> list = new LinkedList<>();
        while (true) {
            try {
                int t = nextInt();
                list.add(t);
            } catch (InputMismatchException e) {
                break;
            }
        }
        int[] a = new int[list.size()];
        Iterator<Integer> it = list.iterator();
        for (int i = 0; it.hasNext(); ++i)
            a[i] = it.next();
        return a;
    }

    public int[] getIntArray1D(int n) {
        int[] array = new int[n];
        for (int i = 0; i < n; ++i) {
            array[i] = nextInt();
        }
        return array;
    }

    public int[][] getIntArray2D(int n, int m) {
        int[][] array = new int[n][m];
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < m; ++j)
                array[i][j] = nextInt();
        }
        return array;
    }

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

    public long[] getAllLongs() {
        List<Long> list = new LinkedList<>();
        while (true) {
            try {
                long t = nextLong();
                list.add(t);
            } catch (InputMismatchException e) {
                break;
            }
        }
        long[] a = new long[list.size()];
        Iterator<Long> it = list.iterator();
        for (int i = 0; it.hasNext(); ++i)
            a[i] = it.next();
        return a;
    }

    public long[] getLongArray1D(int n) {
        long[] array = new long[n];
        for (int i = 0; i < n; ++i) {
            array[i] = nextLong();
        }
        return array;
    }

    public long[][] getLongArray2D(int n, int m) {
        long[][] array = new long[n][m];
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < m; ++j)
                array[i][j] = nextLong();
        }
        return array;
    }

    public int nextChar() {
        int c = readSkipSpace();
        if (c < 0)
            throw new InputMismatchException();
        return c;
    }

    public String nextLine(int initialCapacity) {
        StringBuilder res = new StringBuilder(initialCapacity);
        int c = readSkipSpace();
        do {
            res.append((char) (c));
            c = read();
        } while (!isEscape(c));
        return res.toString();
    }

    @Override
    public void close() throws IOException {
        in.close();
    }
}

class OutputWriter implements Flushable, AutoCloseable {
    private byte[] buf;
    private final int capacity;
    private int count;
    private OutputStream out;

    public OutputWriter(OutputStream stream) {
        this(stream, 10_000);
    }

    public OutputWriter(OutputStream stream, int capacity) {
        if (capacity < 0)
            throw new IllegalArgumentException("capacity < 0");
        out = stream;
        this.capacity = capacity;
        if (capacity != 0) {
            buf = new byte[capacity];
        }
    }

    public void write(int b) throws IOException {
        if (capacity != 0) {
            if (count >= capacity)
                flushBuffer();
            buf[count++] = (byte) b;
        } else {
            out.write(b);
        }
    }

    public void write(byte[] bytes, int off, int len) throws IOException {
        if (capacity != 0) {
            if (len >= capacity) {
                flushBuffer();
                out.write(bytes, off, len);
                return;
            }
            if (len > capacity - count)
                flushBuffer();
            System.arraycopy(bytes, off, buf, count, len);
            count += len;
        } else out.write(bytes, off, len);
    }

    public void write(byte[] bytes) throws IOException {
        write(bytes, 0, bytes.length);
    }

    public void println() throws IOException {
        print("\n");
    }

    public void print(Object object) throws IOException {
        write(String.valueOf(object).getBytes());
    }

    public void println(Object object) throws IOException {
        print(object);
        println();
    }

    public void print(int... ints) throws IOException {
        print(" ", ints);
    }

    public void println(int... ints) throws IOException {
        print(ints);
        println();
    }

    public void println(String separator, int... ints) throws IOException {
        print(separator, ints);
        println();
    }

    public void print(String separator, int... ints) throws IOException {
        if (ints.length == 0) throw new IllegalArgumentException("ints.length == 0");
        for (int i = 0; i < ints.length; ++i) {
            if (i != 0) print(separator);
            print(ints[i]);
        }
    }

    private void flushBuffer() throws IOException {
        if (count > 0) {
            out.write(buf, 0, count);
            count = 0;
        }
    }

    @Override
    public void flush() throws IOException {
        flushBuffer();
        out.flush();
    }

    @Override
    public void close() throws IOException {
        flush();
        out.close();
    }
}

