Definition: Given a negotiation between two participants, answer 'Yes' if both participants agree to the deal, otherwise answer 'No'.
Input: THEM: if i can have the book and hat, you can have everything else.  YOU: how about i trade a ball for the book?  THEM: if i have to give up the book, i'd need 3 balls.  YOU: a ball for the hat instead then?  THEM: same thing. if i have to give up the ball or hat, i'd need 3 balls  YOU: ok, you can have 3 balls if i get the hat  THEM: very well.
Output:
Yes