#include <bits/stdc++.h>

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = std::int64_t;
using P = std::tuple<int,int>;

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int N, K;
    std::cin >> N >> K;

    ll n;

    if(N < K){
        n = 0;
    }else{
        n = 1ll << (N - K);
    }

    std::cout << n << std::endl;
}