#!/usr/bin/python
# -*- coding: utf-8 -*-

'''
https://projecteuler.net/problem=28

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?

= 669171001
'''

import time
import math
import sys
from euler import *

start_time = time.clock()

m = 1001
# m = 5

n = (m - 1) / 2

print 1 + 4 * ((2 * n - 1) * 2 * n * (2 * n + 1) / 6) + 20 * (n * (n + 1) / 2)
# '''
print time.clock() - start_time


