If you need to take Math 115A, take it with Prof. Do! His lectures and notes are very clear and his subtle jokes made the class engaging despite that it was at 9am. His homeworks are long but are very useful since similar problems are used on tests. The exams are fair as they mostly have similar problem types to those covered in class, though a few problems are designed to be “curveballs.” Whenever a problem is too hard, he gives everyone extra points on the tests. Also, he is very helpful during office hours and helps you to significantly improve your proofs. I would totally recommend this class with Prof. Do!