#include "bits/stdc++.h" using namespace std; using ll = long long; const double pi = acos(-1); #define FOR(i,a,b) for (ll i=(a),__last_##i=(b);i<__last_##i;i++) #define RFOR(i,a,b) for (ll i=(b)-1,__last_##i=(a);i>=__last_##i;i--) #define REP(i,n) FOR(i,0,n) #define RREP(i,n) RFOR(i,0,n) #define __GET_MACRO3(_1, _2, _3, NAME, ...) NAME #define rep(...) __GET_MACRO3(__VA_ARGS__, FOR, REP)(__VA_ARGS__) #define rrep(...) __GET_MACRO3(__VA_ARGS__, RFOR, RREP)(__VA_ARGS__) template ostream& operator<<(ostream& os, const vector& v) { REP(i, v.size()) { if (i)os << " "; os << v[i]; }return os; } template ostream& operator<<(ostream& os, const vector>& v) { REP(i, v.size()) { if (i)os << endl; os << v[i]; }return os; } const ll INF = 1LL << 60; ll MOD = 1000000007; ll _MOD = 1000000009; double EPS = 1e-10; #define int long long inline void my_io() { std::ios::sync_with_stdio(false); std::cin.tie(0); cout << fixed << setprecision(16); //cout << setprecision(10) << scientific << ans << endl; } signed main() { ll n, k; cin >> n >> k; ll x = n - k; if (x < 0) { cout << 0 << endl; } else { ll now = 1; while (x > 0) { now *= 2; x--; } cout << now << endl; } }