#include <bits/stdc++.h>
using namespace std;
signed main() {
  long long int arr[58] = {0}, sum = 0;
  long long int n;
  cin >> n;
  for (long long int i = 1; i < 56; i++) {
    long long int s = pow(2, i);
    arr[i] = arr[i - 1] + s;
  }
  cout << arr[n];
}

### Prompt

Construct a Cpp code solution to the problem outlined:

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;
signed main() {
  long long int arr[58] = {0}, sum = 0;
  long long int n;
  cin >> n;
  for (long long int i = 1; i < 56; i++) {
    long long int s = pow(2, i);
    arr[i] = arr[i - 1] + s;
  }
  cout << arr[n];
}

```