#include <bits/stdc++.h>
using namespace std;
inline void frepik() {}
const int dx[] = {1, 0, 0, -1, -1, 1, -1, 1};
const int dy[] = {0, 1, -1, 0, -1, 1, 1, -1};
const int root = (int)1;
const int N = (int)1e5 + 1;
const int logN = (int)log2(N) + 1;
const int inf = (int)(1u << 31) - 1u;
const long long INF = (long long)(1ull << 63) - 1ull;
inline int nextInt() {
  int e;
  scanf("%d", &e);
  return e;
}
inline long long nextLong() {
  long long e;
  scanf("%I64d", &e);
  return e;
}
int main() {
  frepik();
  printf("%I64d", (1LL << nextInt() + 1LL) - 2LL);
  return 0;
}

### Prompt

In CPP, your task is to solve 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;
inline void frepik() {}
const int dx[] = {1, 0, 0, -1, -1, 1, -1, 1};
const int dy[] = {0, 1, -1, 0, -1, 1, 1, -1};
const int root = (int)1;
const int N = (int)1e5 + 1;
const int logN = (int)log2(N) + 1;
const int inf = (int)(1u << 31) - 1u;
const long long INF = (long long)(1ull << 63) - 1ull;
inline int nextInt() {
  int e;
  scanf("%d", &e);
  return e;
}
inline long long nextLong() {
  long long e;
  scanf("%I64d", &e);
  return e;
}
int main() {
  frepik();
  printf("%I64d", (1LL << nextInt() + 1LL) - 2LL);
  return 0;
}

```