#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, zeros = 0, ones = 0;
  string s;
  cin >> n >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] == '0')
      zeros++;
    else
      ones++;
  }
  cout << abs(zeros - ones);
  return 0;
}
