#include <iostream>
#include <cmath>
typedef long long ll;
using namespace std;

int main() {
    int N,K;
    cin>>N>>K;
    if (N < K) {
        cout << 0 << endl;
    } else {
        ll result = pow(2, N - K);
        cout << result << endl;
    }
    return 0;
}