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

namespace AreaOfFigures
{
    class AreaOfFigures
    {
        static void Main(string[] args)
        {
            string area = Console.ReadLine();
            double square = 1;
            if (area == "square")
            {
                double sideSquare = double.Parse(Console.ReadLine());
                square = sideSquare * sideSquare;
                Console.WriteLine("{0:f3}" , square);
            }
            else if (area == "rectangle")
            {
                double rectangleSideA = double.Parse(Console.ReadLine());
                double rectangleSideB = double.Parse(Console.ReadLine());
                square = rectangleSideA * rectangleSideB;
                Console.WriteLine("{0:f3}", square);
            }
            else if (area == "circle")
            {
                double circleRadius = double.Parse(Console.ReadLine());
                square = Math.PI * circleRadius * circleRadius;
                Console.WriteLine("{0:f3}", square);
            }
            else if (area == "triangle")
            {
                double lengthSide = double.Parse(Console.ReadLine());
                double heigthSide = double.Parse(Console.ReadLine());
                square = lengthSide * heigthSide / 2;
                Console.WriteLine("{0:f3}", square);
            }
            else
            {
                Console.WriteLine("Wrong area");
            }
        }
    }
}