#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repb(i, a, b) for(int i = a; i >= b; i--)
// #define FOR(i, a) for(auto& i : a)
#define all(a) a.begin(), a.end()
#define int long long
using namespace std;

signed main(){
    int n, k, ans = 0;
    cin >> n >> k;
    if(k != 1){
        ans = 1;
        rep(i, 0, n - k) ans *= 2;
    }else{
        rep(i, 3, n + 1){
            int tmp = 1;
            rep(j, 0, i - 2) tmp *= 2;
            ans += tmp - 1;
        }
    }
    cout << ans << endl;
}