10 years ago, when I was in high school, I had a book "Guiding High School Mathematics", and I first learned the name of Teacher Sun. It is not an ordinary teaching aid, but expounds the principles and knowledge of the Institute of Mathematics from the internal relations. Very useful! A book that benefited a lot, and later gave it to my brother!

It is really rare to take a class for six years and send most students to key universities. Unfortunately, Mr. Sun is gone.