import java.io.*;
import java.util.StringTokenizer;

class Main{

static final PrintWriter out=new PrintWriter(System.out);

public static void main(String[] args) throws IOException{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String line="";
while((line=br.readLine())!=null&&!line.isEmpty()){
StringTokenizer st= new StringTokenizer(line);
int n=Integer.parseInt(st.nextToken());
int k=Integer.parseInt(st.nextToken());
int ans=0;
int[] ice=new int[n];
line=br.readLine();
for(int i=0;i<n;i++) ice[i]=line.charAt(i)-'0';
int eat=0;
while(true){
ans++;
eat+=1+ice[(ans-1)%n];
if(eat>=k) break;
}
out.println(ans);
out.flush();
}
}
}