#include<iostream>
#include<string>

using namespace std;

#define NMAX 50

int main(){

	int N;
	long long K;
	string S;
	long long data[NMAX];
	long long eatdata[NMAX];

	cin>>N>>K;
	cin>>S;

	for(int i=0;i<N;i++){
		long long ice=1;
		long long eat=0;
		int now=i;
		while(ice!=0){
			ice--;
			ice+=S[now]-'0';
			eat++;
			now++;
			if(now==N) now=0;
			if(eat==N+2){
				eat=K;
				break;
			}
		}
		data[i]=eat;
	}

	cout<<endl;
	int nw=0;
	int c=0;
	int eatc=0;
	for(int i=0;i<N;i++) eatdata[i]=-1;
	while(1){
		if(eatc>=K) break;
		if(eatdata[nw]!=-1){
			break;
		}
		eatdata[nw]=c;
		c++;
		eatc+=data[nw];
		nw+=data[nw];
		nw%=N;
	}
	//cout<<K<<","<<eatc<<","<<c<<","<<nw<<","<<eatdata[nw]<<endl;
	int need=K-eatc;
	int scic=c-eatdata[nw];
	int sci=need/N;
	if(eatc<K) c+=sci*scic;
	if(eatc<K) eatc+=sci*N;
	while(1){
		if(eatc>=K) break;
		c++;
		eatc+=data[nw];
		nw+=data[nw];
		nw%=N;
	}

	cout<<c<<endl;
}