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>.
// @uthor -: puneet
// TimeStamp -: 10:23 AM - 1/10/19 

import java.io.*;
import java.math.BigInteger;
import java.util.InputMismatchException;

public class ZeroOne implements Runnable {


    public void solve() {
        int n=in.ni();
        char[] arr=in.ns().toCharArray();
        int one=0,zero=0;
        for(char c:arr){
            if(c=='0')
                zero++;
            else
                one++;
        }

        int ans=Math.max(zero,one);
        ans-=Math.min(zero,one);
        out.println(ans);
    }

    /* -------------------- Templates and Input Classes -------------------------------*/

    @Override
    public void run() {
        try {
            init();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        solve();
        out.flush();
    }

    private FastInput in;
    private PrintWriter out;

    public static void main(String[] args) throws Exception {
        new Thread(null, new ZeroOne(), "Main", 1 << 27).start();
    }

    private void init() throws FileNotFoundException {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        if (System.getProperty("ONLINE_JUDGE") == null) {
            outputStream = new FileOutputStream("/home/puneet/Desktop/output.txt");
            inputStream = new FileInputStream("/home/puneet/Desktop/input.txt");
        }
        out = new PrintWriter(outputStream);
        in = new FastInput(inputStream);
    }

    public long ModPow(long x, long y, long MOD) {
        long res = 1L;
        x = x % MOD;
        while (y >= 1) {
            if ((y & 1) > 0) res = (res * x) % MOD;
            x = (x * x) % MOD;
            y >>= 1;
        }
        return res;
    }

    public int gcd(int a, int b) {
        if (a == 0) return b;
        return gcd(a % b, a);
    }

    public long gcd(long a, long b) {
        if (a == 0) return b;
        return gcd(b % a, a);
    }

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

        public FastInput(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 ni() {
            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 nl() {
            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 ns() {
            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 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(ns());
            } catch (NumberFormatException e) {
                throw new InputMismatchException();
            }
        }

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

        public double nd() {
            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, ni());
                }
                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, ni());
                    }
                    if (c < '0' || c > '9') {
                        throw new InputMismatchException();
                    }
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }


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

        public SpaceCharFilter getFilter() {
            return filter;
        }

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

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

        public int[] intarr(int n) {
            int arr[] = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = ni();
            }
            return arr;
        }

        public double[] doublearr(int n) {
            double arr[] = new double[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nd();
            }
            return arr;
        }

        public double[][] doublearr(int n, int m) {
            double[][] arr = new double[n][m];
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    arr[i][j] = nd();
                }
            }
            return arr;
        }

        public int[][] intarr(int n, int m) {
            int[][] arr = new int[n][m];
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    arr[i][j] = ni();
                }
            }
            return arr;
        }


        public long[][] longarr(int n, int m) {
            long[][] arr = new long[n][m];
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    arr[i][j] = nl();
                }
            }
            return arr;
        }

        public long[] longarr(int n) {
            long arr[] = new long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nl();
            }
            return arr;
        }

    }

}