# Hexagonal Numbers

Time Limit: 2 seconds

Memory Limit: 256 megabytes

## Description

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.

## Sample Input

Input3Output15Input6Output66

## Sample Output

None

None

None