This book contains more than 500 exercise, divided into six categories: (1) Warmups are execises that every reader shoulr try to do when first reading the material. (2) Basics are exercises to develop facts that are best learned by trying one's own derivation rather that by reading somebody else's. (3) Homework exercises are problems intended to deepen an understanding of material in the current chapter. (4) Exam problems typically involve ideas from two or more chapters simultaneously; they are generally intended for use in take-home exams (not for in-class exams under time pressure). (5) Bonus problems go beyond what an average student of concrete mathematics is expected to handle while taking a course based on this book; they extend the text in interesing ways. (6) Research problems may or may not be humanly solvable, but the ones presented here seem to be worth a try (without time preassure).