#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 1;
const int MOD = 1e9 + 7;
const int INF = 1e9 + 7;
const int EPS = 1e-6;
long long a[MAXN], b[MAXN];
vector<int> g[MAXN], v;
bool used[MAXN];
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  ;
  long long n, m, k, cnt = 0, sum = 0, mx = 0, mn = INF;
  bool y = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cnt += (1ll << i);
  }
  cout << cnt;
  return 0;
}

### Prompt

Please formulate 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 int MAXN = 1e5 + 1;
const int MOD = 1e9 + 7;
const int INF = 1e9 + 7;
const int EPS = 1e-6;
long long a[MAXN], b[MAXN];
vector<int> g[MAXN], v;
bool used[MAXN];
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  ;
  long long n, m, k, cnt = 0, sum = 0, mx = 0, mn = INF;
  bool y = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cnt += (1ll << i);
  }
  cout << cnt;
  return 0;
}

```