#P171B. Star

    ID: 8966 Type: RemoteJudge 2000ms 256MiB Tried: 4 Accepted: 0 Difficulty: 4 Uploaded By: Tags>*special problemcombinatorics*1300

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Description

The input contains a single integer a (1 ≤ a ≤ 18257).

Print a single integer output (1 ≤ output ≤ 2·109).

Input

The input contains a single integer a (1 ≤ a ≤ 18257).

Output

Print a single integer output (1 ≤ output ≤ 2·109).

2

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