#!/usr/bin/env python
"""
Created on 3 Jan 2020

@author: David Doblas Jiménez
@email: daviddoji@pm.me

Solution for problem 028 of Project Euler
https://projecteuler.net/problem=28
"""

from utils import timeit


@timeit("Problem 028")
def compute():
    """
    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?
    """

    size = 1001  # Must be odd
    ans = 1  # Special case for size 1
    step = 0
    i, current = 1, 1
    while step < size - 1:
        step = i * 2
        for _ in range(1, 5):
            current += step
            ans += current
        i += 1

    return ans


if __name__ == "__main__":
    print(f"Result for Problem 028: {compute()}")