import java.util.*;

public class Main {
   public static void main(String[] args) throws Exception {
       Scanner koko = new Scanner(System.in);
       int n = koko.nextInt();
       long k = koko.nextInt();
       String s = koko.next();
       int had=0;
       int paid=0;
       int atari=0;
       int i=0;
       while(had<k){
           paid++;
           if(atari>0){
               paid--;
               atari--;
           }
           if(s.charAt(i%n)=='0'){
               had++;
           }else if(s.charAt(i%n)=='1'){
               had++;
               atari++;
           }else if(s.charAt(i%n)=='2'){
               had++;
               atari+=2;
           }
           i++;
       }
       System.out.println(paid);
   }       
}