#include <bits/stdc++.h>
using namespace std;
long long int power(long long int a, long long int n) {
  long long int res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a, n--;
    else
      a = a * a, n /= 2;
  }
  return res;
}
void solve() {
  long long int n;
  cin >> n;
  long long int ans = 0;
  for (long long int i = n; i >= 1; i--) {
    ans += power(2, i);
  }
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int t = 1;
  while (t--) {
    solve();
  }
}

### Prompt

Generate 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 int power(long long int a, long long int n) {
  long long int res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a, n--;
    else
      a = a * a, n /= 2;
  }
  return res;
}
void solve() {
  long long int n;
  cin >> n;
  long long int ans = 0;
  for (long long int i = n; i >= 1; i--) {
    ans += power(2, i);
  }
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int t = 1;
  while (t--) {
    solve();
  }
}

```