import java.util.*;
import java.io.*;

public class Main {
	public static void main(String[] args) throws Exception {
		new Main().run();
	}

	void run() throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		System.out.println(n >= k ? 1L << (n - k) : 0);
	}

	void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}

}