#include <bits/stdc++.h>
using namespace std;
long long expo(long long x, long long n, long long m) {
  if (n == 0)
    return 1;
  else if (n % 2 == 0)
    return expo((x * x) % m, n / 2, m);
  else
    return (x * expo((x * x) % m, (n - 1) / 2, m)) % m;
}
string DtoB(int j) {
  string s = "";
  for (int i = 32; i >= 0; i--) {
    int k = j >> i;
    if (k & 1)
      s += "1";
    else
      s += "0";
  }
  return s;
}
void solve() {
  int n;
  cin >> n;
  long long k = pow(2, n + 1) - 2;
  cout << k << endl;
  return;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t;
  t = 1;
  while (t--) solve();
  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 expo(long long x, long long n, long long m) {
  if (n == 0)
    return 1;
  else if (n % 2 == 0)
    return expo((x * x) % m, n / 2, m);
  else
    return (x * expo((x * x) % m, (n - 1) / 2, m)) % m;
}
string DtoB(int j) {
  string s = "";
  for (int i = 32; i >= 0; i--) {
    int k = j >> i;
    if (k & 1)
      s += "1";
    else
      s += "0";
  }
  return s;
}
void solve() {
  int n;
  cin >> n;
  long long k = pow(2, n + 1) - 2;
  cout << k << endl;
  return;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t;
  t = 1;
  while (t--) solve();
  return 0;
}

```