#include <bits/stdc++.h>
int main() {
  long long int n, i, j, x = 1;
  long long int sum = 0;
  scanf("%lld", &n);
  for (i = 1; i <= n; i++) {
    for (j = 1; j <= i; j++) {
      x = x * 2;
    }
    sum = sum + x;
    x = 1;
  }
  printf("%lld\n", sum);
  return 0;
}

### Prompt

In Cpp, your task is to solve 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>
int main() {
  long long int n, i, j, x = 1;
  long long int sum = 0;
  scanf("%lld", &n);
  for (i = 1; i <= n; i++) {
    for (j = 1; j <= i; j++) {
      x = x * 2;
    }
    sum = sum + x;
    x = 1;
  }
  printf("%lld\n", sum);
  return 0;
}

```