THEM: hey what do you want?  YOU: you first  THEM: both books  YOU: i can give you 1 book and a hat  THEM: what about a book and ball?  YOU: both books then  THEM: i'll give you 2 balls for 2 books  YOU: i'll give you 2 books and i'll take the rest...  THEM: hmmm i'll give you the 2 balls and 1 hat  YOU: nope  THEM: ok whatever 2 books for everything.