import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double c = scan.nextDouble();
        double rin = scan.nextDouble();
        double rout = scan.nextDouble();
        double pai = 3.14159265;
		double ans = 2 * pai * pai * rin * rin * rout;
        System.out.println(ans * c);
    }
}