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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;
long long a;
int main() {
  scanf("%lld", &a);
  printf("%lld", 1 + 12 * (a * (a - 1) / 2));
  return 0;
}
