import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int K = scan.nextInt();
		String S = scan.next();
		int l = S.length();
		int k = 0;
		if(K <= N) {
			int cnt = 0;
			int a = 0;
			for(int i = 0; i < N; i++) {
				if(a == 0) {
					cnt++;
				}else {
					a--;
				}
				if(K <= 0) {
					break;
				}
				if(S.charAt(i) == '1') {
					a++;
					K--;
				}else if(S.charAt(i) == '2') {
					K -= 2;
					a+=2;
				}
			}
			System.out.println(cnt);
			System.exit(0);
		}
		int a = 0;
		int cnt = 0;
		for(int i = 0; i < N; i++) {
			if(S.charAt(i) == '2') {
				a += 2;
			}else if(S.charAt(i) == '1') {
				a ++;
			}
		}
		if(a >= l) {
			cnt = 0;
			a = 0;
			for(int i = 0; i < N; i++) {
				if(a == 0) {
					cnt++;
				}else {
					a--;
				}
				if(S.charAt(i) == '1') {
					a++;
					K--;
				}else if(S.charAt(i) == '2') {
					K -= 2;
					a += 2;
				}
			}
			System.out.println(cnt);
			System.exit(0);
		}
		cnt = 0;
		int t = l - a;
		int c = 0;
		int d = 0;
		for(int i = 0; i < N; i++) {
			if(d == 0) {
				c++;
			}else {
				d--;
			}
			if(S.charAt(i) == '1') {
				d++;
			}else if(S.charAt(i) == '2') {
				d += 2;
			}
		}
		if(K % N == 0) {
			int ans = t * (K / N - 1) + c;
			System.out.println(ans);
		}else {
			int b = K / N;
			int res = K - b * N;
			for(int i = 0; i < res; i++) {
				if(d == 0) {
					c++;
				}else {
					d--;
				}
				if(S.charAt(i) == '1') {
					d++;
				}else if(S.charAt(i) == '2') {
					d += 2;
				}
			}
			int ans = (b - 1) * (N - 1) + c;
			System.out.println(ans);
		}

	}
}