F. Isosceles triangles
time limit per test
1 second
memory limit per test
512 megabytes
input
standard input
output
standard output

You are given a regular polygon with $$$n$$$ vertices. You should find the number of isosceles triangles with vertices that are the vertices of the polygon.

Input

The only line of input contains one integer $$$n$$$ — the number of vertices of a regular polygon ($$$3 \le n \le 10^9$$$).

Output

The output line should contain a single integer — the number of isosceles triangles with vertices that are the vertices of the polygon.

Examples
Input
3
Output
1
Input
5
Output
10
Note

An isosceles triangle is a triangle that has at least two equal sides.