#include <bits/stdc++.h>
using namespace std;
const long long N = 1e6 + 1;
map<long long, long long> mp, pm;
deque<long long> v, vc, ve;
deque<long long> p, pe;
deque<string> ts, ss;
deque<float> sd;
long long a, b, c, d, e, f, cnt, ans, r, n, l;
double q, t, cnt1;
string g, h, w, o, z, m, s;
char y, u;
bool re, rt;
set<long long> st;
vector<pair<long long, long long> > pr, rp;
int main() {
  cin.tie(NULL);
  cout.tie(NULL);
  ios_base::sync_with_stdio(0);
  cin >> a;
  b = a - 1;
  c = b - 1;
  cnt += b * 4;
  cnt += 4 * (c * (c + 1) / 2);
  cnt++;
  cout << cnt;
}

### Prompt

Construct a Cpp code solution to the problem outlined:

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;
const long long N = 1e6 + 1;
map<long long, long long> mp, pm;
deque<long long> v, vc, ve;
deque<long long> p, pe;
deque<string> ts, ss;
deque<float> sd;
long long a, b, c, d, e, f, cnt, ans, r, n, l;
double q, t, cnt1;
string g, h, w, o, z, m, s;
char y, u;
bool re, rt;
set<long long> st;
vector<pair<long long, long long> > pr, rp;
int main() {
  cin.tie(NULL);
  cout.tie(NULL);
  ios_base::sync_with_stdio(0);
  cin >> a;
  b = a - 1;
  c = b - 1;
  cnt += b * 4;
  cnt += 4 * (c * (c + 1) / 2);
  cnt++;
  cout << cnt;
}

```