Codeforces_556A

// Codeforces 556A

#include <cstring>
#include <iostream>

using namespace std;

int main()
{
    int n, nn, zer = 0, one = 0;
    string str;
    cin >> n >> str;
    char mass[n];
    strcpy(mass, str.c_str());
    for( int i = 0; i < n; i++ )
    {
        if( mass[i] == '1' ){one++;}
        else{zer++;}
    }
    if( one > zer ){cout<<one-zer;}
    else{cout<<zer-one;}
    return 0;
}