#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second

#define endl '\n'
#define IOS()                     \
	ios_base::sync_with_stdio(0); \
	cin.tie(0)

#define rep(i, s, n) for (int i = s; i < n; i++)
#define rrep(i, s, n) for (int i = (n)-1; i >= (s); i--)
const long long MOD = 1000000007, INF = 1e18;
string get_str(string s)
{
	s += ',';
	string ret = "";
	for (int i = 0; i < s.size(); i++)
	{
		if (s[i] == ',')
			ret += "=%ld, ";
		else
			ret += s[i];
	}
	return ret;
}
#define dump(...)                                       \
	printf(get_str(#__VA_ARGS__).c_str(), __VA_ARGS__); \
	cout << endl
//******************************************************************************

template <typename T>
vector<T>
make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts>
auto make_v(size_t a, Ts... ts)
{
	return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type
fill_v(T &t, const V &v) { t = v; }

template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type
fill_v(T &t, const V &v)
{
	for (auto &e : t)
		fill_v(e, v);
}

template <class T>
inline bool chmin(T &a, T b)
{
	if (a > b)
	{
		a = b;
		return true;
	}
	return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
	if (a < b)
	{
		a = b;
		return true;
	}
	return false;
}

int N;
int dp[2020][2];

signed main()
{
	int N, K;
	cin >> N >> K;
	if (N < K)
	{
		cout << 0 << endl;
		return 0;
	}
	cout << (1ll << (N - K)) << endl;
}