#include<iostream>
#include<algorithm>
#include<string>
using namespace std;

/****************/
//蟻本を読もう！//
/****************/
#define INF (1LL << 44)

typedef long long Int;

Int n, k;
string s;
Int solve(int x){
	int now = x;
	int res = 1;
	int cnt = 500;
	while(res){
		if(cnt-- == 0)return INF;
		res--;
		res += s[x] - '0';
		x++;
		x%=n;
	}
	return (x+n-1-now)%n+1;
}

Int go[33][54];

int main(){
	cin >> n >> k >> s;
	for(int i = 0;i < n;i++){
		go[0][i] = solve(i);
	}	
	for(int i = 1;i < 33;i++){
		for(int j = 0;j < 50;j++){
			Int ne = (go[i-1][j] + j) % n;
			go[i][j] = go[i-1][j] + go[i-1][ne];
			go[i][j] = min(go[i][j], INF);
		}
	}
	
	int res = 0, now = 0;
	for(int i = 32;i >= 0;i--){
		if(k >= go[i][now]){
			k -= go[i][now];
			now += go[i][now];
			now %= n;
			res += 1LL << i;
		}
	}
	if(k)res++;
	cout << res << endl;
	return 0;	
}