codeforces#P162A. Pentagonal numbers
Pentagonal numbers
Description
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.
The only line of input contains an integer n (1 ≤ n ≤ 100).
Output the n-th pentagonal number.
Input
The only line of input contains an integer n (1 ≤ n ≤ 100).
Output
Output the n-th pentagonal number.
Samples
2
5
5
35