#include <bits/stdc++.h>   using namespace std;   const int NMAX = 100005;   int n, k;   char s[NMAX];   int sum[NMAX];   int get(int l, int r) {     l = max(1, l);     r = min(r, n);     return sum[r] - sum[l - 1];   }   int main() {     cin.sync_with_stdio(false);     cin >> n >> k;     cin >> (s + 1);     for (int i = 1; i <= n; i++) sum[i] = sum[i - 1] + (s[i] ==  0 );     int ans = 1 << 30;     for (int i = 1; i <= n; i++)       if (s[i] ==  0 ) {         int l = 1;         int r = n;         int sol = -1;         while (l <= r) {           int mi = (l + r) / 2;           if (get(i - mi, i - 1) + get(i + 1, i + mi) >= k) {             sol = mi;             r = mi - 1;           } else             l = mi + 1;         }         if (sol != -1) ans = min(ans, sol);       }     cout << ans;     return 0;   }   