using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Area_of_Figures
{
    class Program
    {
        static void Main(string[] args)
        {
            string typeOfFigure = Console.ReadLine();

            if (typeOfFigure == "square")
            {
                double parameterForArea = double.Parse(Console.ReadLine());
                double area = parameterForArea * parameterForArea;
                Console.WriteLine($"{area:F3}");
            }
            else if (typeOfFigure== "rectangle")
            {

                int sideA = int.Parse(Console.ReadLine());
                double sideB = double.Parse(Console.ReadLine());

                double resultArea = sideA * sideB;

                Console.WriteLine($"{resultArea:F3}");
            }
            else if (typeOfFigure=="circle")
            {
                double r = double.Parse(Console.ReadLine());

                double area = 2 * Math.PI * r;

                Console.WriteLine($"{area:F3}");
            }
            else if (typeOfFigure=="triangle")
            {
                double lend = double.Parse(Console.ReadLine());
                double H = double.Parse(Console.ReadLine());

                double area = 0.5 * lend * H;

                Console.WriteLine($"{area:F3}");
            }

        }
    }
}