using System;

public class Program

{

    public static void Main()

    {

        string figure = Console.ReadLine();

        if (figure == "square") 

        {

            double a = double.Parse(Console.ReadLine());

            Console.WriteLine("{0:F3}", a * a);

        }

        else if (figure == "rectangle")

        {

            double a = double.Parse(Console.ReadLine());

            double b = double.Parse(Console.ReadLine());

            Console.WriteLine("{0:F3}", a*b);

        }

        else if (figure == "circle")

        {

            double r = double.Parse(Console.ReadLine());

            Console.WriteLine("{0:F3}", 2*3.14*r);

        }

        else 

        {

            double a = double.Parse(Console.ReadLine());

            double b = double.Parse(Console.ReadLine());

            Console.WriteLine("{0:F3}", a*b/2);

        }

    }

}