using System;

public class Program

{

    public static void Main()

    {

        //-----------------------------------------------------

        Console.WriteLine("Input diameter: ");

        double input = Convert.ToDouble(Console.ReadLine());

        Console.WriteLine();

        Console.WriteLine("1. Keliling");

        Console.WriteLine("2. Luas");

        Console.WriteLine();

​

        Console.WriteLine("Pilih menu: ");

        string menu = Console.ReadLine();

        double pi = 3.14D;

        double r = input / 2;

        double luas;

        double keliling;

​

        if (menu == "1")

        {

            luas = pi * input;

            Console.WriteLine(luas);

        } else if (menu == "2") {

            keliling = pi * r * r;

            Console.WriteLine(keliling);

        }

    }

}