Sam has been appointed as the new Librarian in a library. He needs to perform the following operations on the N books arranged in the bookshelves to get a unique combination of books:

• He must select a K-length contiguous sequence of books from the bookshelf.
• He must then remove the books that were chosen.
• Then he needs to merge the remaining books and determine whether the resulting sequence is unique.
• He has to repeat this operation for all possible contiguous segments of books from the N books on the bookshelf.

Given an array A which represents the N books in the bookshelves, your task is to help Sam find and return an integer value representing all the possible unique combinations of books that can be generated.