#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int mod = 1e9 + 7;
const int inf = (1 << 30) - 1;
const ll infll = (1LL << 61) - 1;

int N, K;

int main()
{
    cin >> N >> K;
    if (N < K)
        cout << 0 << "\n";
    else
        cout << (1 << (N - K)) << "\n";
}