using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

namespace _11.Geometry_Calculator

{

    class Program

    {

        static void Main(string[] args)

        {

            string figureType = Console.ReadLine();

​

            if (figureType == "triangle")

            {

                Triangle();

            }

            else if(figureType == "square")

            {

                Square();

            }

            else if (figureType == "rectangle")

            {

                Rectangle();

            }

            else if (figureType == "circle")

            {

                Circle();

            }

​

        }

​

        private static void Circle()

        {

            double radius = int.Parse(Console.ReadLine());

​

            double area = Math.PI * Math.Pow(radius, 2);

​

            Console.WriteLine($"{area:F2}");

        }

​

        private static void Rectangle()

        {

            double width = int.Parse(Console.ReadLine());

            double hight = int.Parse(Console.ReadLine());

​

            double area = width * hight;

​

            Console.WriteLine($"{area:F2}");

​

        }

​

        private static void Square()

        {

            double side = int.Parse(Console.ReadLine());

​

            double area = Math.Pow(side, 2);

​

            Console.WriteLine($"{area:F2}");

​

        }

​

        private static void Triangle()

        {

            double side = int.Parse(Console.ReadLine());

            double hight = int.Parse(Console.ReadLine());

​

            double area = side * hight /2 ;

​

            Console.WriteLine($"{area:F2}");

        }

    }

}

​