#include <bits/stdc++.h>
using namespace std;

int main() {
    int N, K;
    string S;
    cin >> N >> K >> S;
    for (auto& c : S)
        c -= '0';

    int ans = 0;
    int free = 0;
    while (K--) {
        static int now = 0;
        if (free) {
            free--;
        } else
            ans++;
        free += S[now++];
        if (now == N) now = 0;
    }

    cout << ans << endl;
}