#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, n, m, ans = 4, sum = 1, temp;
  cin >> n;
  if (n == 1) {
    cout << "1" << endl;
    return 0;
  } else {
    for (i = 1; i < n; i++) {
      sum = sum + ans;
      ans = ans + 4;
    }
  }
  cout << sum << endl;
}

### Prompt

Your task is to create a CPP solution to the following problem:

While playing with geometric figures Alex has accidentally invented a concept of a n-th order rhombus in a cell grid.

A 1-st order rhombus is just a square 1 × 1 (i.e just a cell).

A n-th order rhombus for all n ≥ 2 one obtains from a n-1-th order rhombus adding all cells which have a common side with it to it (look at the picture to understand it better).

<image>

Alex asks you to compute the number of cells in a n-th order rhombus.

Input

The first and only input line contains integer n (1 ≤ n ≤ 100) — order of a rhombus whose numbers of cells should be computed.

Output

Print exactly one integer — the number of cells in a n-th order rhombus.

Examples

Input


1


Output


1

Input


2


Output


5

Input


3


Output


13

Note

Images of rhombus corresponding to the examples are given in the statement.

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, n, m, ans = 4, sum = 1, temp;
  cin >> n;
  if (n == 1) {
    cout << "1" << endl;
    return 0;
  } else {
    for (i = 1; i < n; i++) {
      sum = sum + ans;
      ans = ans + 4;
    }
  }
  cout << sum << endl;
}

```