//
//	CS212 Java method
//
//	Author: ???
//	Instructor: John Wang
//
//	Goal: Thie progrsm will read a file containing scores and name ...
//

import java.util.Scanner;
import java.text.DecimalFormat;
class Method_0
{
	public static void main(String[] args)
	{
		DecimalFormat f1 = new DecimalFormat("0.0");
		Scanner input = new Scanner(System.in);

		while(input.hasNextInt())
		{
			int radius = input.nextInt();
			double area = AreaOfCircle(radius);
			System.out.println(f1.format(area));
		}

		System.out.println("Done.");
	}
	//-----------
	public static double AreaOfCircle(double r)
	{
		double area = Math.PI * r * r;
		return area;
	}
}