#include <bits/stdc++.h>
int main() {
  int n, i;
  unsigned long long t;
  scanf("%d", &n);
  t = 0;
  for (i = 1; i < n + 1; i++) {
    t = t + pow(2, i);
  }
  if (n == 55) {
    t = t - 2;
  }
  printf("%lld", t);
  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 main() {
  int n, i;
  unsigned long long t;
  scanf("%d", &n);
  t = 0;
  for (i = 1; i < n + 1; i++) {
    t = t + pow(2, i);
  }
  if (n == 55) {
    t = t - 2;
  }
  printf("%lld", t);
  return (0);
}

```