#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

tuple<int, int, int> solve(const string& s, int eat, int hit)
{
    int n = s.size();
    int buy = 0;
    for(int i=0; i<n; ++i){
        if(eat == 0)
            break;
        if(hit > 0)
            -- hit;
        else
            ++ buy;
        hit += s[i] - '0';
        -- eat;
    }
    return make_tuple(buy, eat, hit);
}

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

    int ret = 0;
    int buy, hit;
    tie(buy, eat, hit) = solve(s, eat, 0);
    ret += buy;
    tie(buy, eat, hit) = solve(s, eat, hit);
    ret += buy;

    int x = eat / n;
    ret += x * buy;
    eat -= x * n;

    tie(buy, eat, hit) = solve(s, eat, hit);
    ret += buy;
    cout << ret << endl;

    return 0;
}