using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}

​

public class RandomClass {

    public void CallExtensionMethod() {

        ExtensionMethod();

    }

    public void CallNonExtensionMethod() {

        CallExtensionMethod();

    }

}

​

public static class Extensions {

        public static void ExtensionMethod(this RandomClass rc) {

}

}