"""

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?
"""

n = (1001+1)/2 # number of circles
sums = 1

for i in range(2, n+1):
	sums += 4*((2*i-1)**2) - 12*(i-1)

print sums