import java.util.Scanner;
import java.lang.Math;

public class test{
	public static void main(String args[]){
	
		double radius;
		double area;
		
		Scanner input = new Scanner(System.in);
		System.out.print("Enter a double value: ");
		radius = input.nextDouble();
		
		//radius = 20;
		
		area = Math.pow(radius, 2) * 3.14159;
		
		System.out.println(area);
		
		
		
		
	}
	
}