AreaOfFigure

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

namespace ConsoleApplication62
{
    class Program
    {
        static void Main(string[] args)
        {
            var figura = Console.ReadLine();
            double area;
            if (figura == "square")
            {
                var a = double.Parse(Console.ReadLine());
                area = a * a;
                Console.WriteLine(Math.Round(area, 3));
            }
            else if (figura == "rectangle")
            {
                var b = double.Parse(Console.ReadLine());
                var c = double.Parse(Console.ReadLine());
                area = b * c;
                Console.WriteLine(Math.Round(area, 3));
            }
            else if (figura == "circle")
            {
                var radius = double.Parse(Console.ReadLine());
                area = Math.PI * radius * radius;
                Console.WriteLine(Math.Round(area, 3));
            }
            else if (figura == "triangle")
            {
                var k = double.Parse(Console.ReadLine());
                var h = double.Parse(Console.ReadLine());
                area = (k * h) / 2.0;
                Console.WriteLine(Math.Round(area, 3));
            }

        }
    }
}