#include <bits/stdc++.h>
using namespace std;
char _;
const int maxN = 80 + 5;
const int maxM = 5000 + 5;
const int mod = 1000 * 1000 * 1000 + 7;
const int base = 701;
const int SQ = 500;
const int maxL = 20;
long double x = 1.000000011;
long double power(long double n, int k) {
  if (k == 0) return 1.0;
  long double ans = power(n, k / 2);
  ans = ans * ans;
  if (k & 1) ans = ans * n;
  return ans;
}
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  cout << (1LL << (n + 1)) - 2 << endl;
  return 0;
}

### Prompt

Your challenge is to write 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;
char _;
const int maxN = 80 + 5;
const int maxM = 5000 + 5;
const int mod = 1000 * 1000 * 1000 + 7;
const int base = 701;
const int SQ = 500;
const int maxL = 20;
long double x = 1.000000011;
long double power(long double n, int k) {
  if (k == 0) return 1.0;
  long double ans = power(n, k / 2);
  ans = ans * ans;
  if (k & 1) ans = ans * n;
  return ans;
}
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  cout << (1LL << (n + 1)) - 2 << endl;
  return 0;
}

```