#include <bits/stdc++.h>
int n;
int main() {
  scanf("%d", &n);
  printf("%lld\n", (1ll << n + 1) - 2);
  return 0;
}

### Prompt

Please formulate 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 n;
int main() {
  scanf("%d", &n);
  printf("%lld\n", (1ll << n + 1) - 2);
  return 0;
}

```