// yukicoder: No.820 Power of Two
// 2019.4.30 bal4u

#include <stdio.h>

int main()
{
	int N, K;
	
	scanf("%d%d", &N, &K);
	if (N < K) puts("0");
	else printf("%lld\n", 1LL << (N-K));
	return 0;
}