Flag Area

Time Limit: 1 sec

 

The Problem

The National flag is the symbol of independence of a nation. As an independent nation, Bangladesh has also a national flag. It contains a red disc almost at the center of green field. The red disc represents the sun rising over Bengal, and also the blood of those people, who died for the independence of Bangladesh. The green field stands for the natural beauty of the land of Bangladesh.

The standard ratio of our flag is 10: 6 (length=10, and width =6) and radius of the red circle is one-fifth (1:5) of the total length of the flag.

 

 

Now find out the area of green part of the flag.

 

The Input

Input file contains a series of lines. Each line contains one integer number W (1<=W<=50), which is the width of the flag. Input is terminated by EOF. [π = 3.1416]

 

The Output

For each line of input, you have to print the area of green part rounded to two decimal places in a separate line.

 

Sample input

10

20

 

Sample output

47.43

189.73

 

 

 

[School Level]

Inter School & College Programming Contest (ISCPC) 2015 

Problem Setter: Souruv Barua