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.

Examples

Input

2


Output

5


Input

5


Output

35

Source: codeforces | Difficulty: EASY
Tags: Implementation


Solutions: