using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

namespace Lica.Figuri

{

    class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine("Enter figure: ");

            var f1 = "square";

            var f2 = "rectangle";

            var f3 = "circle";

            var f4 = "triangle";

            var figure = Console.ReadLine();

​

            if (figure == f1)

            {

                Console.WriteLine("side = ");

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

                var area = side * side;

                Console.WriteLine("sguare area = " + area);

            }

            else if (figure == f2)

            {

                Console.WriteLine("a =");

                Console.WriteLine("b = ");

                var a = int.Parse(Console.ReadLine());

                var b = int.Parse(Console.ReadLine());

                var area1 = a * b;

                Console.WriteLine("rectangle area = " + area1); 

            }  

            else if (figure == f3)

            {

                Console.WriteLine("r = ");

                var r = int.Parse(Console.ReadLine());

                var area2 = Math.PI * r * r;

                Console.WriteLine("circle area = " + area2);

            }

            else if (figure == f4)

            {

                Console.WriteLine("a1 = ");

                Console.WriteLine("h = ");

                var a1 = double.Parse(Console.ReadLine());

                var h = double.Parse(Console.ReadLine());

                var area3 = (a1 * h / 2);            

                Console.WriteLine(Math.Round(area3, 3));

            }

            else

            {

                Console.WriteLine("wrong figure");

            }

       }               

    }

}

​