#include<iostream> #include<iomanip> #include<vector> #include<algorithm> #include<set> #include<map> #include<unordered_map> #include<stack> #include<queue> #include<math.h> #include<functional> #include<bitset> #include<cassert> using namespace std; using lint = long long; using ld = long double; using pint = pair<int, int>; using plint = pair<lint, lint>; #define MOD 998244353LL #define INF 1000000000LL #define EPS 1e-10 #define FOR(i,n,m) for(lint i=n;i<(int)m;i++) #define REP(i,n) FOR(i,0,n) #define DUMP(a) REP(d,a.size()){cout<<a[d];if(d!=a.size()-1)cout<<" ";else cout<<endl;} #define ALL(v) v.begin(),v.end() #define UNIQUE(v) sort(ALL(v));v.erase(unique(ALL(v)),v.end()); #define pb push_back int main() { cin.tie(0); ios::sync_with_stdio(false); int n, k; cin >> n >> k; if(n < k) { cout << 0 << endl; } else { int ans = 1; REP(i, n - k) ans *= 2; cout << ans << endl; } return 0; } /* --------------------------------------- */