#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<long long> dp(56, 0);
  dp[1] = 2;
  for (long long i = 2; i < 56; i++) {
    dp[i] = dp[i - 1] + (pow(2, i));
  }
  dp[55] -= 2;
  long long n;
  cin >> n;
  cout << dp[n];
  return 0;
}

### Prompt

Please provide a CPP coded solution to the problem described below:

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;
int main() {
  vector<long long> dp(56, 0);
  dp[1] = 2;
  for (long long i = 2; i < 56; i++) {
    dp[i] = dp[i - 1] + (pow(2, i));
  }
  dp[55] -= 2;
  long long n;
  cin >> n;
  cout << dp[n];
  return 0;
}

```