using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var s = AddClasses(("hello", true), ("ignore-me", false), ("add-me", true));

        Console.WriteLine(s);

    }

    public static string AddClasses(params (string s, bool b)[] classes){

        return String.Join(" ", classes.Where(c => c.b).Select(c => c.s));

    }

}