【讲解】：发奋时候竟忘记吃饭，快乐时候就忘记了忧愁，把自己就要老了这件事也不放在心上，如此罢了。”

To understand the arithmetic of algebraic varieties is to understand the symmetries hidden within them.

We not only need to build good cars, but also sell them well, and more importantly, provide good service.