#include <bits/stdc++.h>
using namespace std;
void logf(istream_iterator<string> it) {}
template <typename T, typename... Args>
void logf(istream_iterator<string> it, T a, Args... args) {
  cout << *it << "=" << a << " ";
  logf(++it, args...);
}
const double PI = acos(-1);
void solve() {
  int n;
  cin >> n;
  ;
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    long long x = 1LL << i;
    ans += x;
  }
  cout << ans << endl;
}
int main() {
  cin.tie(nullptr);
  std::ios::sync_with_stdio(false);
  solve();
}

### Prompt

Create a solution in cpp for the following problem:

The numbers of all offices in the new building of the Tax Office of IT City will have lucky numbers.

Lucky number is a number that consists of digits 7 and 8 only. Find the maximum number of offices in the new building of the Tax Office given that a door-plate can hold a number not longer than n digits.

Input

The only line of input contains one integer n (1 ≤ n ≤ 55) — the maximum length of a number that a door-plate can hold.

Output

Output one integer — the maximum number of offices, than can have unique lucky numbers not longer than n digits.

Examples

Input

2


Output

6

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
void logf(istream_iterator<string> it) {}
template <typename T, typename... Args>
void logf(istream_iterator<string> it, T a, Args... args) {
  cout << *it << "=" << a << " ";
  logf(++it, args...);
}
const double PI = acos(-1);
void solve() {
  int n;
  cin >> n;
  ;
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    long long x = 1LL << i;
    ans += x;
  }
  cout << ans << endl;
}
int main() {
  cin.tie(nullptr);
  std::ios::sync_with_stdio(false);
  solve();
}

```