#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
// ***********************
// for debug
#define DEBUGe
// -----------

#define NOP do{}while(0)
#ifdef DEBUG
#define TRACE(...) do{printf(__VA_ARGS__);fflush(stdout);}while(0)
#define TRACECR do{putchar_unlocked('\n');fflush(stdout);}while(0)
#else
#define TRACE(...) NOP
#define TRACECR NOP
#endif

#define	mypc(d)	putchar_unlocked(d)
#define PRINCR mypc('\n')
#define NOCR(strig) do{char *p;p=strchr(strig,'\n');if(p)*p='\0';}while(0)
// The out-of-date function
#define	asctime(...)	asctime_s(...)
#define	ctime(...)		ctime_s(...)
#define	strlen(a)	mystr_len(a)
//#define	fopen(...)		fopen_s(...)
//#define	freopen(...)	freopen_s(...)
//#define	rewind(a)		fseek(a,0L,SEEK_SET)
//#define	setbuf(a,b)		setvbuf(a,b,_IOFBF,BUFSIZ)

// for stdio
#define GETLINE(str) do{char *p;fgets(str,sizeof(str),stdin);p=strchr(str,'\n');if(p)*p='\0';}while(0)
#define mygc(c) (c)=getchar_unlocked()
static char *GETWORD(char* str) {char c;char *cp;cp=&str[0];mygc(c);while(c!=EOF){if((c==' ')||(c=='\n'))break;*cp++=c;mygc(c);}*cp='\0';return &str[0];}
#define	GETINTS(a,b) {char s[34];int *ap=a;REP(i,b){GETWORD(s);*ap++=atoi(s);}}
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		atarimoto;
	int		end;

	box = GETWORDINT();
	want = GETWORDLONG();
	GETLINE(str);
	// 先ず一周してみる
	idx = -1;
	while( eat < want ) {
		idx++;
		if( idx >= box ) break;
		if( atari ) {
			atari--;
			tada++;
		} else {
			buyed++;
		}
		atari += str[idx] - '0';
		eat++;
	}
	if( atari ) {
		TRACE("当たりが継続する\n");
		idx = -1;
		tada = 0;
		atarimoto = atari;
		while( eat < want ) {
			idx++;
			if( idx >= box ) break;
			if( atari ) {
				atari--;
				tada++;
			} else {
				buyed++;
			}
			atari += str[idx] - '0';
			eat++;
		}
		atarimoto = atari - atarimoto;
		TRACE("２周めで増える量 %d\n", atarimoto );
		if( tada != box ) {
			TRACE("買う必要がある\n");
			buy1box = box - tada;
			TRACE("２周めで買った数 %d\n", buy1box);
			end = (want - eat ) / box -1 ;
			TRACE("箱買いする量 %d\n", end * box);
			eat += box * end;
			TRACE("残りの量 %d\n", want - eat );
			buyed += buy1box * end;
			atari += atarimoto * end;
			while( eat < want ) {
				idx++;
				if( idx >= box ) idx = 0;
				if( atari ) {
					atari--;
					tada++;
				} else {
					buyed++;
				}
				atari += str[idx] - '0';
				eat++;
			}
		} else {
			TRACE("買う必要がない\n");
		}
	} else {
		TRACE("当たりは継続しない\n");
		buy1box = box - tada;
		end = (want-eat) / box -1;
		eat += box * end;
		buyed += buy1box * end;
		while( eat < want ) {
			idx++;
			if( idx >= box ) idx = 0;
			if( atari ) {
				atari--;
				tada++;
			} else {
				buyed++;
			}
			atari += str[idx] - '0';
			eat++;
		}
	}
	printf("%ld\n", buyed );
	return 0;
}