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

int main()
{
    int n, k; cin>>n>>k;
    string s; cin>>s;

    int ice=0, buy=0, win=0;
    while (k>0) {
        for(auto& c: s) {
            win==0 ?  buy++ : win--;
            win+=c-'0';
            ice++;
            k--;
            if (k==0) return !printf("%d\n", buy);
        }
        if (win>=n) k=0;
    }
    printf("%d\n", buy);
}