#include <bits/stdc++.h>

using namespace std;

int main() {
  long long n, k, res = 0, r = 0;
  string s;
  cin >> n >> k >> s;
  while (k) {
    for (int i = 0; i < (int)s.size(); ++i) {
      if (r) --r;
      else ++res;
      r += s[i] - '0';
      --k;
      if (k == 0) break;
    }
  }
  cout << res << endl;
}