Problem Description

A positive even number $ A $ is given.

Among the positive integers $ x $, $ y $ such that $ x + y = A $, choose the pair that maximizes $x \times y$ and output that value.

Input Format

The input is given from the standard input in the following format:

$ A $

• The first line contains a positive even number $ A $ ( $2 \leq A \leq 100$ ).

Output Format

Output the maximum value of $x \times y$. End the output with a newline.

Sample Input and Output

Sample Input #1

10

Sample Output #1

25

Sample Input #2

60

Sample Output #2

900

Notes/Hints

Sample Explanation 1

When $ x = 5 $, $ y = 5 $, $x \times y = 25$, which is the maximum value.

见题面 Input 部分

见题面 Output 部分