Intersecting Points in Polygon

Time Limit: 1 sec

 

The Problem

A Polygon is a geometric figure that is bounded by a finite chain of straight line segment. These segments are called its edge or side and the point where the two edge meet are called vertex. Some polygons are given below.

 

Here 8-gon says that the polygon contains 8 sides. Now your task is to draw a n-gon polygon so that a straight line can intersect maximum number of its sides.

 

Example: 8-gon

 

The Input

There are several lines of input. Each line contain the number of side of a polygon N (3<=N<=10^17).

 

The Output

For each input just produce one output which is the maximum number of intersecting sides.

 

Sample Input

4

8

 

Sample Output

4

8

 

 

 

Problem Setter: Milton Deb