#include <bits/stdc++.h>
using namespace std;
long long n, now, power;
signed main() {
  scanf("%lld", &n);
  now = 2, power = 2;
  for (long long i = 2; i <= n; i++) {
    now += power * 2;
    power *= 2;
  };
  printf("%lld\n", now);
}

### 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>
using namespace std;
long long n, now, power;
signed main() {
  scanf("%lld", &n);
  now = 2, power = 2;
  for (long long i = 2; i <= n; i++) {
    now += power * 2;
    power *= 2;
  };
  printf("%lld\n", now);
}

```