<image>

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
n = int(input().split()[0])
print((2 * n - 1) * (2 * n - 1) + 4 * (n - 1) * n // 2)