Crystal Ball Sequence
Description
Crystal ball sequence on hexagonal lattice is defined as follows: n-th element is the number of lattice points inside a hexagon with (n + 1) points on each side. The formula is Hn = 3·n·(n + 1) + 1. You are given n; calculate n-th element of the sequence.
The only line of input contains an integer n (0 ≤ n ≤ 9).
Output the n-th element of crystal ball sequence.
Input
The only line of input contains an integer n (0 ≤ n ≤ 9).
Output
Output the n-th element of crystal ball sequence.
Samples
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7
3
37