import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        if (n < k) {
            System.out.println(0);
        } else {
            System.out.println(pow(2, n - k));
        }
    }
    
    static int pow(int x, int p) {
        if (p == 0) {
            return 1;
        } else {
            return x * pow(x, p - 1);
        }
    }
}