using System;

using System.Text;

public class Program

{

    public static void Main()

    {

        StringBuilder sb = new StringBuilder("Default Text");

        Console.WriteLine($"Before function call: {sb.ToString()}");

        AppendString(sb);

        Console.WriteLine($"After function call: {sb.ToString()}");

    }

    public static void AppendString(StringBuilder sb)

    {

        sb.Append(" Hello world");

        Console.WriteLine($"Inside function: {sb.ToString()}");

    }

}