Spiral Diagonal
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We can make a 5 by 5 spiral pattern by writing the positive integers, starting in the center and moving to the right in a clockwise pattern as shown below.

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

The sum of the diagonal entries is 21 + 7 + 1 + 3 + 13 = 45.

Write a programme to find the sum of the diagonal entries in an (2k+1) by (2k+1) spiral pattern.

Input
-----

The input will be several integer values for k (0 <= k <= 2^16).
The end of the input will be indicated by a value k=-1, which should not
be processed.

Output
------

For each k, output the sum of the diagonal entries.

Sample Input
------------

2
5
100
-1

Sample Output
-------------

45
451
2707001