#include <bits/stdc++.h>
using namespace std;
long long fastpow(long long a, long long b, long long c) {
  long long res = a;
  while (c) {
    if (c & 1) res = (res * b);
    b = (b * b);
    c >>= 1;
  }
  return res;
}
int main() {
  long long n, ans;
  cin >> n;
  ans = fastpow(1, 2, (n + 1));
  cout << (ans - 2) << endl;
  return 0;
}

### 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 fastpow(long long a, long long b, long long c) {
  long long res = a;
  while (c) {
    if (c & 1) res = (res * b);
    b = (b * b);
    c >>= 1;
  }
  return res;
}
int main() {
  long long n, ans;
  cin >> n;
  ans = fastpow(1, 2, (n + 1));
  cout << (ans - 2) << endl;
  return 0;
}

```