using System;

​

public class Program

{

    public static void Main()

    {

        Contar20();

    }

​

    public static void Contar20()

    {

        int i = 0;

        while (i <= 20)

        {

            if (i % 2 == 0)

            {

                Console.WriteLine(i);

            }

            i++;

        }

    }

}