#include <bits/stdc++.h>
using namespace std;
long long n, t;
long long ans = 0;
long double m = 1.000000011;
long double pow(long double a, long long b) {
  if (b == 1) {
    return a;
  }
  if (b % 2 == 0) {
    return pow(a * a, b / 2);
  } else {
    return pow(a * a, b / 2) * a;
  }
}
int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cin >> n;
  t = 1;
  for (int i = 1; i <= n; i++) {
    t *= 2;
    ans += t;
  }
  cout << ans;
}

### 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 n, t;
long long ans = 0;
long double m = 1.000000011;
long double pow(long double a, long long b) {
  if (b == 1) {
    return a;
  }
  if (b % 2 == 0) {
    return pow(a * a, b / 2);
  } else {
    return pow(a * a, b / 2) * a;
  }
}
int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cin >> n;
  t = 1;
  for (int i = 1; i <= n; i++) {
    t *= 2;
    ans += t;
  }
  cout << ans;
}

```