#include <bits/stdc++.h>
using namespace std;
signed main() {
  long long t = 1;
  while (t--) {
    long long n;
    cin >> n;
    long long s = 0;
    for (long long i = n; i >= 1; i--) {
      long long x = pow(2, i);
      s += x;
    }
    cout << s;
  }
}

### 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;
signed main() {
  long long t = 1;
  while (t--) {
    long long n;
    cin >> n;
    long long s = 0;
    for (long long i = n; i >= 1; i--) {
      long long x = pow(2, i);
      s += x;
    }
    cout << s;
  }
}

```