#include<bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
main(){
    int N,K;
    cin >> N >> K;
    int cnt = 1 << (N - K);
    if(K == 1)cnt -= N;
    cout << cnt << endl;
}