A lot of book friends have reported that they have been tired of reading recently, but in fact, the author is also tired of writing, and he needs to find a lot of information, and he has to understand the content of it, and there can be no logical errors. The foreshadowing of these chapters is very necessary, if it is not foreshadowing, it will be very abrupt to win the highest prize in mathematics later. It's already the last chapter of something so professional, and the last chapter, I hope to be able to write a little more relaxed. C