//O(K)の愚直解

#include "stdio.h"

int main(){
	int n;
	int k;
	int v[1000];
	char s[100];
	
	int m;
	int block;
	int rem;
	int x;
	int y;
	
	int ans = 0;
	int p = 0;
	int i,j;
	int q = 0;
	
	scanf("%d %d\n%s", &n, &k, s);
	
	m = (200/n) * n;
	block = k/m;
	rem = k%m;
	x = (m/4) * 4;
	y = m%x;
	
	for(i = j = 0; i<m; ++i, ++j){
		if(j==n) j=0;
		v[i] = (s[j] - '0');
	}


	for(i=0; i<block; ++i){
		for(j=0; j<x; j+=4){
			if(p == 0) ++ans;
			else --p;
			p += v[j];
			
			if(p == 0) ++ans;
			else --p;
			p += v[j+1];
			
			if(p == 0) ++ans;
			else --p;
			p += v[j+2];
			
			if(p == 0) ++ans;
			else --p;
			p += v[j+3];
		}
		for(j=0; j<y; ++j){
			if(p == 0) ++ans;
			else --p;
			p += v[x+j];
		}
		if(p>=n) break;
	}
	for(i=0; i<rem; ++i){
		if(p == 0) ++ans;
		else --p;
		p += v[i];
	}

	printf("%d\n", ans);
	return 0;
}