#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long x;
  cin >> x;
  if (x == 1)
    cout << x * 2 << endl;
  else {
    long long sum = 0;
    for (long long i = 1; i <= x; i++) {
      sum += pow((long long)2, i);
    }
    cout << sum << endl;
  }
}

### 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() {
  unsigned long long x;
  cin >> x;
  if (x == 1)
    cout << x * 2 << endl;
  else {
    long long sum = 0;
    for (long long i = 1; i <= x; i++) {
      sum += pow((long long)2, i);
    }
    cout << sum << endl;
  }
}

```