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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.

#### Constraints

#### 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`

## Comments