# -*- coding: utf-8 -*-
"""
Created on Sat Mar  4 16:18:14 2017
@author: Cesar Alvarez
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?
"""
import time
starttime = time.time()

Numbers=[a for a in range(1,2000000)]
Diagonals=[0,0,0,1]
FinalRange=1001
step=2
while Diagonals[-4::3][1]-Diagonals[-4::3][0] != (FinalRange-1) * 3:
    start=Diagonals[-1]+(step-1)
    stop=Diagonals[-1]+step*4
    Diagonals.extend(Numbers[start:stop:step])
    step+=2
    print(step)
print('sumatory={}'.format(sum(Diagonals)))
print('time={}'.format(time.time() - starttime))

