#include <stdio.h>

int N, K;

typedef long long ll;

ll pow(int n);

ll ans;

int main() {

	scanf("%d %d", &N, &K);

	if (K == 1) {
		ans = pow(N - 1) - N;
	}
	else {
		ans = pow(N-K);
	}

	printf("%lld\n", ans);

	return 0;
}
ll pow(int n) {

	ll r = 1;

	int i;

	for (i = 1; i <= n; i++) {
		r *= 2;
	}
	return r;
}