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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 n;
  long long int s;
  scanf("%d", &n);
  s = 6 * n * (n - 1) + 1;
  printf("%I64d", s);
  return 0;
}
