## Observing Frogs

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Points: 5 (partial)
Time limit: 0.1s
Java 0.5s
Memory limit: 16M

Author:
Problem type

Lyestria is observing a group of frogs. The frogs are numbered from to .

The frog numbered conveniently lives at the point . On this day, the frog numbered wants to go to the point , where all the points are equally spaced.

Lyestria then asks you to compute the sum of the distances each frog must travel to get to their desired location.

#### Input Specification

The first line contains one integer, , the number of frogs.

#### Output Specification

On one line, output one integer, the sum of the distances each frog must travel to get home.

#### Sample Input

4

#### Sample Output

8

#### Sample Input 2

5

#### Sample Output 2

12