#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

const long long INF = 1LL<<50;

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  long long k;
  string s;
  cin >> n >> k >> s;

  vector<vector<long long> > dp(50, vector<long long>(n));

  for (int i = 0; i < n; i++) {
    long long cnt = 0;
    int r = 1;
    int j = i;

    while (r > 0) {
      if (++cnt > n) break;
      --r;
      r += s[j] - '0';
      ++j %= n;
    }

    if (cnt > n)
      dp[0][i] = INF;
    else
      dp[0][i] = cnt;
  }

  for (int i = 1; i < 50; i++) {
    for (int j = 0; j < n; j++) {
      dp[i][j] = min(dp[i-1][j] + dp[i-1][(j + dp[i-1][j]) % n], INF);
    }
  }

  int cur = 0;
  long long ret = 0;
  for (int i = 49; i >= 0; i--) {
    if (k > dp[i][cur]) {
      k -= dp[i][cur];
      ret += 1LL<<i;
      cur = (cur + dp[i][cur]) % n;
    }
  }
  cout << ++ret << endl;
    
  return 0;
}