#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%i", &n);
  long long arr[n];
  arr[0] = 2;
  for (int i = 1; i < n; i++) arr[i] = arr[i - 1] * 2;
  long long ans = 0;
  for (int i = 0; i < n; i++) ans += arr[i];
  cout << ans << endl;
}

### Prompt

Generate a Cpp solution to 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;
int main() {
  int n;
  scanf("%i", &n);
  long long arr[n];
  arr[0] = 2;
  for (int i = 1; i < n; i++) arr[i] = arr[i - 1] * 2;
  long long ans = 0;
  for (int i = 0; i < n; i++) ans += arr[i];
  cout << ans << endl;
}

```