AreaOfFigures

using System;

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

            if (figure == "square")
            {
                double squareSide = double.Parse(Console.ReadLine());
                Console.WriteLine($"{squareSide * squareSide:F3}");
            }
            if (figure == "rectangle")
            {
                double reactangleSide1 = double.Parse(Console.ReadLine());
                double reactangleSide2 = double.Parse(Console.ReadLine());
                Console.WriteLine($"{reactangleSide1 * reactangleSide2:f3}");
            }
            if (figure == "circle")
            {
                double circleRadius = double.Parse(Console.ReadLine());
                Console.WriteLine($"{(circleRadius * circleRadius) *Math.PI:F3}");
            }
            if (figure == "triangle")
            {
                double triangleSide1 = double.Parse(Console.ReadLine());
                double triangleSide2 = double.Parse(Console.ReadLine());

                Console.WriteLine($"{(triangleSide1 * triangleSide2) / 2:F3}");

            }





        }
    }
}