300845: CF162A. Pentagonal numbers

Memory Limit：256 MB Time Limit：3 S
Judge Style：Text Compare Creator：
Submit：0 Solved：0

Description

A. Pentagonal numberstime limit per test3 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard output

Pentagonal numbers are figurate numbers which can be calculated using the formula pn = (3n2 - n) / 2 (always integer). You are given n; calculate n-th pentagonal number.

Input

The only line of input contains an integer n (1 ≤ n ≤ 100).

Output

Output the n-th pentagonal number.

ExamplesInput
2
Output
5
Input
5
Output
35

Input

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