#P470A. Crystal Ball Sequence

    ID: 3082 Type: RemoteJudge 2000ms 256MiB Tried: 0 Accepted: 0 Difficulty: (None) Uploaded By: Tags>*special problemimplementation*1400

Crystal Ball Sequence

No submission language available for this problem.

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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