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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 ans = 1, n;
  scanf("%d", &n);
  for (int i = 1; i < n; i++) ans += 12 * i;
  printf("%d\n", ans);
  return 0;
}
