#include <iostream>
#include <string>
using namespace std;
int main(){
    int n;
    string str, res;
    cin>>n>>str;
    //找规律 模拟
    int j = 0;
    for(int i = 0; i < n; ++i){
       str[j++] = str[i];
      while(j >= 2 && ((str[j-1]=='1' && str[j-2]=='0')||(str[j-1]=='0' && str[j-2]=='1'))) j-=2;
    }
    cout<<j<<endl;
    return 0;
}