#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  int n;
  cin >> n;
  string s;
  cin >> s;
  int one = 0;
  int ans = 0;
  for (char c : s) {
    if (c == '1') {
      if (one) ans++;
      one ^= 1;
    } else if (c != '9') ans++;
  }
  cout << ans << '\n';
  return 0;
}