#include"bits/stdc++.h"

using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

#define FOR(k,m,n) for(ll (k)=(m);(k)<(n);(k)++)
#define REP(i,n) FOR((i),0,(n))
#define WAITING(str) int str;std::cin>>str;
#define DEBUGING(str) cout<< #str << " " str<<endl

constexpr int INF = (1 << 30);
constexpr ll INFL = (1ll << 60);
constexpr ll MOD = 1000000007;// 10^9+7



int main()
{
	int N, K;
	cin >> N >> K;

	ll res;
	if (N < K) {
		res = 0;
	}
	else {
		res = 1;
		REP(i, N - K)res *= 2;
	}
	cout << res << endl;
	return 0;
}