import java.util.*;

public class No411{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		int k = sc.nextInt();
		if(k == 1){
			System.out.println(0);
			return;
		}

		System.out.println((int)Math.pow(2, n-k));
	}
}