"""
Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:

21 22 23 24 25
20  7  8  9 10
19  6  1  2 11
18  5  4  3 12
17 16 15 14 13

It can be verified that the sum of the numbers on the diagonals is 101.

What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed in the same way?
"""

# Idea use recursion


def sol(n):
    if n == 0:
        return 1
    else:
        return 4 * (2 * n + 1) ** 2 - 12 * n + sol(n - 1)


print(sol(500))
