#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <string>
#include <queue>
#include <stack>
#include <math.h>
#include <set>
#include <cstdio>
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define P pair<int, int>

#define MOD 1000000007
#define INF 1012345678
#define NINF (-2147483647-1)
#define LLINF 9223372036854775807
using ll = long long;
using namespace std;

//pow(int)
int pow(int k, int n) {
    int x = 1;
    while (n > 0) {
        if (n & 1) {
            x *= k;
        }
        k *= k;
        n >>= 1;
    }
    return x;
}

int main() {
    int N, K;
    cin >> N >> K;
    if (N < K) {
        cout << 0 << endl;
    }
    else {
        cout << pow(2, N - K) << endl;
    }
    getchar(); getchar();
    return 0;
}