#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; double w; };

ll MOD = 10000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N, K; cin >> N >> K;
	string S; cin >> S;
	int atari = 0, prev_atari = 0, buy = 0, prev_buy = 0, eat = 0, prev_eat = 0;
	for (;;) {
		for (int i = 0; i < N; i++) {
			if (eat >= K) {
				cout << buy << endl;
				return 0;
			}
			if (atari > 0) atari--;
			else buy++;
			atari += S[i] - '0';
			eat++;
		}
		if (atari >= N) {
			cout << buy << endl;
			return 0;
		}
		if (atari == prev_atari) {
			int x = (K - eat) / (eat - prev_eat);
			buy += x * (buy - prev_buy);
			eat += x * (eat - prev_eat);
		}
		prev_atari = atari;
		prev_buy = buy;
		prev_eat = eat;
	}
}