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

### Prompt

Your task is to create 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>
int main() {
  long long int a, i, j, k = 1;
  scanf("%lld", &a);
  for (i = 1; i <= a; i++) {
    k = k * 2;
  }
  k = 2 * (k - 1);
  printf("%lld\n", k);
  return 0;
}

```