#include <bits/stdc++.h>
using namespace std;
unsigned long long binpow(unsigned long long p, unsigned long long n) {
  if (n == 0) {
    return 1;
  }
  unsigned long long res = binpow(p, n / 2);
  if (n % 2) {
    return p * res * res;
  }
  return res * res;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  unsigned long long n{};
  cin >> n;
  n = n + 1;
  unsigned long long x;
  unsigned long long l{2};
  x = binpow(l, n);
  x -= 2;
  cout << x << "\n";
  return 0;
}

### Prompt

Your task is to create 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;
unsigned long long binpow(unsigned long long p, unsigned long long n) {
  if (n == 0) {
    return 1;
  }
  unsigned long long res = binpow(p, n / 2);
  if (n % 2) {
    return p * res * res;
  }
  return res * res;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  unsigned long long n{};
  cin >> n;
  n = n + 1;
  unsigned long long x;
  unsigned long long l{2};
  x = binpow(l, n);
  x -= 2;
  cout << x << "\n";
  return 0;
}

```