#include <bits/stdc++.h>
using namespace std;
int N, K;
int main() {
	cin >> N >> K;
	int ret = 1;
	for(int i = 0; i < N - K; i++) ret *= 2;
	if(K != 1) cout << ret << endl;
	else cout << ret - N + K - 1 << endl;
	return 0;
}