import java.util.ArrayList;
import java.util.HashSet;
import java.util.Scanner;


public class Main {
	static int N, K;
	static String S;
			
	static private void solve()
	{
		int buybar = 0;
		int nextbar = 0;
		int freebar = 0;
		
		for (int k = 1; k <= K; k++) {
			if (freebar > 0) 
				freebar--;
			else 
				buybar++;
			
			switch (S.charAt(nextbar)) {
			case '0': break;
			case '1': freebar++;  break;
			case '2': freebar+=2; break;
			}
			
			nextbar++;
			if (nextbar == N) {
				nextbar = 0;
			}
		}
		
		System.out.println(buybar);
	}
	
	static public void main(String[] args)
	{
		Scanner sca = new Scanner(System.in);
		
		N = sca.nextInt();
		K = sca.nextInt();
		S = sca.next();
		
		solve();
	}
}