Since you started out valid, you can handle this incrementally, rather than dealing with both old code and your new code at the same time.
因为开始时是有效的，所以您可以逐步处理，而不是同时处理旧代码和新代码。
2
Of course, by the time you're 80, there will be 65 more years of new books, so by then, you're dealing with 315 years of books, which allows you to read about 20 books from each year.