import java.util.*;
 
public class uppg_02 {
 
        public static void main(String[] args) {
                Scanner sc = new Scanner(System.in);
               
                System.out.println("ange cirkelns radie");
               
                double radie = sc.nextDouble();
               
                double area = radie*radie*Math.PI;
               
                System.out.println(area);
 
        }
 
}
