In a pile of reading material, there are novels, story-books, dramas and comics.
Every novel has a drama next to it, every story-book has a comic next to it and there is no story-book next to novel.
If there be a novel at the top and the number of books be 40, the order of the books in the pile is :
Clearly the sequence is :
novel, drama, story-book, comic i.e. ndsc