#include <bits/stdc++.h>
using namespace std;
long long x[100];
void run() {
  x[1] = 2;
  for (int i = 2; i < 56; i++) {
    x[i] = x[i - 1] + pow(2, i);
  }
}
int main() {
  run();
  long long n;
  while (~scanf("%I64d", &n)) {
    printf("%I64d\n", x[n]);
  }
}

### Prompt

Create a solution in Cpp for 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 x[100];
void run() {
  x[1] = 2;
  for (int i = 2; i < 56; i++) {
    x[i] = x[i - 1] + pow(2, i);
  }
}
int main() {
  run();
  long long n;
  while (~scanf("%I64d", &n)) {
    printf("%I64d\n", x[n]);
  }
}

```