using System;

public class Program

{

    public static void Main()

    {

        string original1 = "Hola mundo1!";

        string original2 = "Hola mundo2!";

        string original3 = "Hola mundo3!";

        string original4 = "Hola mundo4!";

        ToUpper1(original1);

        ToUpper2(ref original2);

        ToUpper3(original3);

        ToUpper4(ref original4);

        Console.WriteLine(original1);

        Console.WriteLine(original2);

        Console.WriteLine(original3);

        Console.WriteLine(original4);

    }

    public static void ToUpper1(string str) 

    {

        str.ToUpper();

    }

    public static void ToUpper2(ref string str) 

    {

        str.ToUpper();

    }

    public static void ToUpper3(string str) 

    {

        str = str.ToUpper();

    }

    public static void ToUpper4(ref string str) 

    {

        str = str.ToUpper();

    }

}