#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0 ; i < (n) ; i++)

#define int long long


signed main(){
	long long N,K;
	cin >> N >> K;
	long long v = (N-K);
	if( K == 1 ){
		cout << (1 << (N - 1)) - N << endl;
		
	}else{
		cout << (1ll<<v) << endl;
	}
	
	
}