#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define all(c) c.begin(), c.end() #define rall(c) c.rbegin(), c.rend() #define debug(x) cerr << #x << ": " << x << endl using namespace std; typedef long long ll; typedef pair Pll; typedef pair Pii; const ll MOD = 1000000007; const long double EPS = 1e-10; const int dyx[4][2] = { { 0, 1}, {-1, 0}, {0,-1}, {1, 0} }; int main() { std::ios::sync_with_stdio(0); cin.tie(0); ll n, k; cin >> n >> k; cout << (n>=k?(1LL << (n-k)):0) << endl; return 0; }