import java.io$.*$;

import java.util.$*$;

import java.text.$*$;

import java.math.$*$;

import java.util.regex.$*$;

public class Main $\{$

static double circleArea$($double radius$)\{$

$//$ WRITE YOUR CODE HERE

$\}$

$/*****$DO NOT CHANGE THE CODE BELOW THIS LINE$*****/$

public static void main$($String$[]$ args$)\{$

Scanner in $=$ new Scanner$($System$.$in$)$;

double a;

a $=$ in$.$nextDouble$()$;

circleArea$($a$)$;

$\}$

$\}$