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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>
int main() {
  int a, b;
  scanf("%d", &a);
  b = 1 + 6 * a * (a - 1);
  printf("%d\n", b);
  return 0;
}
