#include <bits/stdc++.h>
using namespace std;
long long int fast_pow(long long int k, long long int p) {
  if (p == 0) return 1;
  long long int P = fast_pow(k, p / 2);
  P = (P * P);
  if (p % 2 == 1) P = (P * k);
  return P;
}
long long int invmod(long long int a, long long int m) {
  return fast_pow(a, m - 2);
}
bool isPrime(long long int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (int i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
long long int nextPowerOf2(long long int n) {
  n >>= 1;
  long long int count = 0;
  if (n && !(n & (n - 1))) return n;
  while (n != 0) {
    n >>= 1;
    count += 1;
  }
  return 1 << count;
}
long long int binomialCoeff(long long int n, long long int k) {
  long long int C[k + 1];
  memset(C, 0, sizeof(C));
  C[0] = 1;
  for (long long int i = 1; i <= n; i++) {
    for (long long int j = min(i, k); j > 0; j--) C[j] = C[j] + C[j - 1];
  }
  return C[k];
}
int main() {
  long long int n;
  cin >> n;
  long long int a[101];
  a[1] = 1;
  a[2] = 5;
  for (int i = 3; i <= n; i++) {
    a[i] = a[i - 1] + 4 * (i - 1);
  }
  cout << a[n] << endl;
}

### Prompt

Develop a solution in CPP to the problem described below:

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;
long long int fast_pow(long long int k, long long int p) {
  if (p == 0) return 1;
  long long int P = fast_pow(k, p / 2);
  P = (P * P);
  if (p % 2 == 1) P = (P * k);
  return P;
}
long long int invmod(long long int a, long long int m) {
  return fast_pow(a, m - 2);
}
bool isPrime(long long int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (int i = 5; i * i <= n; i = i + 6)
    if (n % i == 0 || n % (i + 2) == 0) return false;
  return true;
}
long long int nextPowerOf2(long long int n) {
  n >>= 1;
  long long int count = 0;
  if (n && !(n & (n - 1))) return n;
  while (n != 0) {
    n >>= 1;
    count += 1;
  }
  return 1 << count;
}
long long int binomialCoeff(long long int n, long long int k) {
  long long int C[k + 1];
  memset(C, 0, sizeof(C));
  C[0] = 1;
  for (long long int i = 1; i <= n; i++) {
    for (long long int j = min(i, k); j > 0; j--) C[j] = C[j] + C[j - 1];
  }
  return C[k];
}
int main() {
  long long int n;
  cin >> n;
  long long int a[101];
  a[1] = 1;
  a[2] = 5;
  for (int i = 3; i <= n; i++) {
    a[i] = a[i - 1] + 4 * (i - 1);
  }
  cout << a[n] << endl;
}

```