text: """
  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?
  
  Solution comment:
  The inclueded numbers are increasing by 2 four times, then increasing by
  4 four times, then by 6 four times... This is done (dim-1)/2 times. For dim=5
  above, this is done 2 times.
  """
  
  n = 1
  s = n
  addon = 0
  for j in range((1001-1)/2):
      addon += 2
      for i in range(4):
          n += addon
          s += n
  print s
  