#include <bits/stdc++.h>
using namespace std;
inline void read(int &first) {
  first = 0;
  while (1) {
    char ch = getchar();
    if (ch == ' ' || ch == '\n') break;
    first = first * 10 + ch - '0';
  }
}
inline void write(int first) {
  char wr[12];
  int k = 0;
  if (!first) ++k, wr[k] = '0';
  while (first) {
    ++k;
    wr[k] = char(first % 10 + '0');
    first /= 10;
  }
  for (int i = k; i >= 1; --i) putchar(wr[i]);
}
const int N = 1e5 + 5;
int n, k, s[N], a[N];
char ch;
bool f(int len) {
  for (int i = 1; i <= n; ++i) {
    if (!a[i]) continue;
    int s1 = s[min(n, i + len)] - s[i - 1];
    int s2 = s[i] - s[max(0, i - len - 1)];
    if (s1 + s2 - a[i] >= k + 1) return 1;
  }
  return 0;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n >> k;
  for (int i = 1; i <= n; ++i)
    cin >> ch, s[i] = s[i - 1] + (ch == '0'), a[i] = ch == '0';
  int l = 1, r = n;
  while (r - l > 1) {
    int mid = (l + r) >> 1;
    if (f(mid))
      r = mid;
    else
      l = mid;
  }
  if (f(l))
    cout << l;
  else
    cout << r;
}
