#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)


typedef long long ll;
ll modpow(ll a, ll n) {
	if (a == 0) return 0;
	ll r = 1;
	while (n) r = r*((n % 2) ? a : 1), a = a*a, n >>= 1;
	return r;
}
//-----------------------------------------------------------------
int main() {
	int N, K;
	while (cin >> N >> K)
	{
		if (K == 1)
			cout << modpow(2, N - 1) - 2 << endl;
		else
			cout << modpow(2, N - K) << endl;
	}
}