#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1000000007;
const long long int N = 100005;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int t, i, j, k;
  t = 1;
  while (t--) {
    long long int a[60] = {0};
    a[1] = 2;
    for (i = 2; i < 56; i++) a[i] = 2 * a[i - 1];
    for (i = 1; i <= 55; i++) a[i] += a[i - 1];
    long long int n;
    cin >> n;
    cout << a[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;
const long long int mod = 1000000007;
const long long int N = 100005;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int t, i, j, k;
  t = 1;
  while (t--) {
    long long int a[60] = {0};
    a[1] = 2;
    for (i = 2; i < 56; i++) a[i] = 2 * a[i - 1];
    for (i = 1; i <= 55; i++) a[i] += a[i - 1];
    long long int n;
    cin >> n;
    cout << a[n];
  }
  return 0;
}

```