#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;
typedef pair<int, int> P;

int n, k;
string s;

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> n >> k >> s;
	ll ret = 0, stock = 0;
	for (int i = 0; i < n && i < k; i++) {
		if (stock == 0) {
			ret++;
			stock += (ll)(s[i]-'0');
		}
		else {
			stock--;
			stock += (ll)(s[i]-'0');
		}
	}
	if (stock >= ret || k <= n) {
		cout << ret << endl;
		return 0;
	}
	k -= n;
	ll ret2 = ret - stock;
	ret += ret2*(k/n);
	k %= n;
	FOR(i, k) {
		if (stock == 0) {
			ret++;
			stock += (ll)(s[i]-'0');
		}
		else {
			stock--;
			stock += (ll)(s[i]-'0');
		}
	}
	cout << ret << endl;
	return 0;
}