#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    long long N,K;
    cin >> N >> K;
    if ( K == 1 ) {
        cout << (1<<(N-2))-1 << endl;
    }
    else {
        cout << (1<<(N-K)) << endl;
    }
    return 0;
}