#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    int a[n];
    rep(i,n)a[i] = s[i] - '0';

    int ans = 0;
    int now = 0;
    if(k < 1000000){
        rep(i,k){
            if(now > 0)now--;
            else ans++;
            now += a[i%n];
        }
    }else{
        rep(i,n){
            if(now > 0)now--;
            else ans++;
            now += a[i%n];
        }
        if(ans == 1 && now > 0){
            cout << 1 << endl;
            return 0;
        }
        k -= n;
        if(now == 0){
            ans += (k / n) * ans;
            k -= (k / n) * n;
            rep(i,k){
                if(now > 0)now--;
                else ans++;
                now += a[i%n];
            }
            cout << ans << endl;
            return 0;
        }

        

        int now2 = now;
        int cnt = 0;
        rep(i,n){
            if(now > 0)now--;
            else cnt++;
            now += a[i%n];
        }
        k -= n;
        ans += cnt;

        if(now == now2){
            ans += (k / n) * cnt;
            k -= (k / n) * n;
            rep(i,k){
                if(now > 0)now--;
                else ans++;
                now += a[i%n];
            }
            cout << ans << endl;
            return 0;
        }

        
        
    }

    cout << ans << endl;
    return 0;
}