300993: CF188A. Hexagonal Numbers

Memory Limit：256 MB Time Limit：2 S
Judge Style：Text Compare Creator：
Submit：0 Solved：0

Description

A. Hexagonal Numberstime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard output

Hexagonal numbers are figurate numbers which can be calculated using the formula hn = 2n2 - n. You are given n; calculate n-th hexagonal number.

Input

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

Output

Output the n-th hexagonal number.

ExamplesInput
3
Output
15
Input
6
Output
66

Input

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