Introduction - If you have any usage issues, please Google them yourself
http://www.patest.cn/contests/pat-a-practise/1022
A Digital Library contains millions of books, stored according to their titles, authors, key words of their abstracts, publishers, and published years. Each book is assigned an unique 7-digit number as its ID. Given any query a reader, you are supposed to output the resulting books, sorted in increasing order of their ID s.