#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll N, K;
    cin >> N >> K;
    if (N < K){
        cout << 0 << endl;
    }else{
        cout << (1LL << (N - K)) << endl;
    }
    return 0;
}