#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
// Yukicoder №78 クジ付きアイスバー ★★☆
// https://yukicoder.me/problems/no/78
// ***********************
#define PRINCR do{printf("\n");fflush(stdout);}while(0)
#define GETLINE(str) do{char *p;fgets(str,sizeof(str),stdin);p=strchr(str,'\n');if(p)*p='\0';}while(0)
#define REP(a,b) for(int a=0;a<(int)(b);++a)
static char *GETWORD(char* str) {char c;char *cp;cp=&str[0];c=fgetc(stdin);while( c != EOF ){if((c==' ')||( c=='\n')) break;*cp++=c;c=fgetc(stdin);}*cp='\0';return &str[0];}
#define	GETINTS(a,b) {char s[34];int *ap=a;REP(i,b){GETWORD(s);sscanf(s,"%d", ap);ap++;}}
static int GETLINEINT(void) {char s[34];GETLINE(s);return atoi(s);}
static int GETWORDINT(void) {char s[34];GETWORD(s);return atoi(s);}
static long GETWORDLONG(void) {char s[34];GETWORD(s);return atol(s);}
#define SWAP(type,a,b) do{type _c;_c=a;a=b;b=_c;}while(0)
int main( void ) {
	char	str[258];
	int		box;
	int		eat,atari;
	int		idx;
	long	want;
	long	buyed = 0;
	int		tada = 0;
	int		buy1box;
	int		end;

	box = GETWORDINT();
	want = GETWORDLONG();
	GETLINE(str);
	idx = -1;
	while( eat < want ) {
		if( atari ) {
			atari--;
			tada++;
		} else {
			buyed++;
		}
		idx++;
		if( idx >= box ) idx = 0;
		atari += str[idx] - '0';
		eat++;
	}
	if( atari ) {
		idx = -1;
		tada = 0;
		while( eat < want ) {
			if( atari ) {
				atari--;
				tada++;
			} else {
				buyed++;
			}
			idx++;
			if( idx >= box ) idx = 0;
			atari += str[idx] - '0';
			eat++;
		}
		if( tada != box ) {
			// 買う必要がある
			buy1box = box - tada;
			end = want / box;
			end = end * box;
			while( eat < end ) {
				eat += box;
				buyed += buy1box;
			}
			while( eat < want ) {
				if( atari ) {
					atari--;
					tada++;
				} else {
					buyed++;
				}
				idx++;
				if( idx >= box ) idx = 0;
				atari += str[idx] - '0';
				eat++;
			}
		}
	} else {
		// 当たりは継続しない
		buy1box = box - tada;
		end = want / box;
		end = end * box;
		while( eat < end ) {
			eat += box;
			buyed += buy1box;
		}
		while( eat < want ) {
			if( atari ) {
				atari--;
				tada++;
			} else {
				buyed++;
			}
			idx++;
			if( idx >= box ) idx = 0;
			atari += str[idx] - '0';
			eat++;
		}
	}
	printf("%ld\n", buyed );
	return 0;
}