#include <bits/stdc++.h>
int main() {
  long long n, i, ans = 0, j, f;
  scanf("%I64d", &n);
  for (i = 1; i <= n; ++i) {
    f = 1;
    for (j = 1; j <= i; ++j) f = f * 2;
    ans += f;
  }
  printf("%I64d", ans);
  return 0;
}

### 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>
int main() {
  long long n, i, ans = 0, j, f;
  scanf("%I64d", &n);
  for (i = 1; i <= n; ++i) {
    f = 1;
    for (j = 1; j <= i; ++j) f = f * 2;
    ans += f;
  }
  printf("%I64d", ans);
  return 0;
}

```