The school lends no more than 500 books to the class for after-school reading. Each class borrows 25 books, which is just in time, and each class borrows 30 books, which is just in time. How many books are there at most?
学校把不超过500册书借给班级课余阅读，每班借25本，正好借完，每班借30本，也正好借完．这批书最多有多少本？
<result>450</result>