Hexagonal Numbers
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.
The only line of input contains an integer n (1 ≤ n ≤ 100).
Output the n-th hexagonal number.
Input
The only line of input contains an integer n (1 ≤ n ≤ 100).
Output
Output the n-th hexagonal number.
Samples
3
15
6
66