#include <bits/stdc++.h>

#include <atcoder/all>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define FAST_IO                \
  ios::sync_with_stdio(false); \
  cin.tie(0);
const i64 INF = 1001001001001001001;
using Modint = atcoder::static_modint<998244353>;


int main() {
  FAST_IO

  int N;
  cin >> N;
  string S;
  cin >> S;


  auto ans = 0;
  int mx = 0;

  int sl = 0;
  int sr = S[0] == '1' ? 1 : -1;

  int msl = 0;

  for (int i = 1; i < N; i ++) {
    sr += S[i] == '1' ? 1 : -1;

    int cur = sr - msl;
    if (cur < 0) {
      S[i] = '1';
      sr += 2;
      ans ++;
    }

    sl += S[i - 1] == '1' ? 1 : -1;
    msl = max(msl, sl);
  }

  cout << ans << endl;
}