Zhang Yu gave detailed lectures, especially calculus. With Zhang Yu's video, the foundation will be solid and the understanding will be profound. After all, Li Yongle belongs to the proposition group, and many questions in it are true and original. Li Yongle's line generation speaks very well. Therefore, I personally think it is suitable for use. Changyu is used for the high number part, and Li Yongle is used for the line generation probability (you can watch it when you have time, but you can focus on it when you don't have time).