#include <bits/stdc++.h>

using namespace std;

struct Initializer {
  Initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15);
  }
} initializer;

int main() {
  int n, k;
  cin >> n >> k;
  cout << (1 << (n - k)) - (k == 1 ? n : 0) << endl;
}