import java.util.Scanner;

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

		int n = sc.nextInt(), k = sc.nextInt(), ans = 1;
		for(int i = k+1; i <= n; i++){
			ans *= 2;
		}
		if(k == 1){
			ans-=n;
		}
		System.out.println(ans);
	}
}