#include <bits/stdc++.h>
using namespace std;
long long int k, n, m, i, x, ar[1000005], res, sum, mk, q, mn, ak[1000005];
int main() {
  scanf("%lld", &n);
  for (int i = 1; i <= n; i++) {
    q = pow(2, i);
    sum += q;
  }
  printf("%lld", sum);
}

### Prompt

Develop a solution in Cpp to the problem described below:

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 int k, n, m, i, x, ar[1000005], res, sum, mk, q, mn, ak[1000005];
int main() {
  scanf("%lld", &n);
  for (int i = 1; i <= n; i++) {
    q = pow(2, i);
    sum += q;
  }
  printf("%lld", sum);
}

```