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Input

The input contains a single integer a (1 ≤ a ≤ 18257).

Output

Print a single integer output (1 ≤ output ≤ 2·109).

Examples

Input

2


Output

13
#include <bits/stdc++.h>
using namespace std;
int main() {
  int depth, solution = 1;
  cin >> depth;
  for (int size = 12; depth > 1; --depth, size += 12) solution += size;
  cout << solution << "\n";
  return 0;
}
