The grandmother of Erin is not Dave. Erin is not smart. Fiona is not rough if Harry is not red. If Erin is not the brother of Harry then Harry is not red. If Erin is not the aunt of Harry then Bob is not blue. Erin is not Harry's aunt if Fiona is not rough. Erin is not Harry's brother if Erin is smart or Dave is Erin's grandmother.