#include <bits/stdc++.h>

using namespace std;

long long solve(long long res, long long r, long long k, string 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;
    }
  }
  return res;
}

int main() {
  long long n, k;
  string s;
  cin >> n >> k >> s;
  long long sum = accumulate(s.begin(), s.end(), 0) - ('0' - 1) * n;
  if (sum >= 2 * n) {
    cout << solve(0, 0, min(n, k), s) << endl;
  } else {
    long long res = (long long)(k / (double)sum * n * (1 - (double)n / sum)) / n * n;
    cout << solve(res, res / n * (sum - n), k - res, s) << endl;
  }
}