import java.io.PrintWriter;
import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		int n=Integer.parseInt(scanner.next());
		long k=Long.parseLong(scanner.next());
		String s=scanner.next();
		long[][] nx=new long[32][51];
		final long INF=(long)1e12;
		for(int i=0; i<n; i++) {
			int sum=0;
			for(int j=i; j<i+n; j++) {
				int x=s.charAt(j%n)-'0';
				sum+=x;
				if(sum+1==j-i+1) {
					nx[0][i]=j+1;
					break;
				}
			}
			if(nx[0][i]==0) {
				nx[0][i]=INF;
			}
		}
		for(int i=1; i<=30; i++) {
			for(int j=0; j<n; j++) {
				long x=nx[i-1][j];
				if(x==INF) {
					nx[i][j]=INF;
				}else{
					nx[i][j]=Math.min(INF, x/n*n+nx[i-1][(int) (x%n)]);
				}
			}
		}
		long ans=0;
		int x=0;
		for(int i=30; i>=0; i--) {
			if(nx[i][x]<k) {
				ans+=(1<<i);
				k-=nx[i][x]/n*n;
				x=(int)(nx[i][x]%n);
			}
		}
		out.println(ans+1);
		out.close();
		scanner.close();
	}
}