Challenge: Paper Collator. Help me make a book.

Hey Lego-people. I make books for my students, about 50 pages per book. I'll print 50 copies of page 1, flip the paper over and print 50 copies of page 2 on the back, then page 3 with 4 one the back etc. Then when I have all these I have to collate them, it's time consuming. I was looking to build a machine, with about 5 slots of A4 paper, that could spit the paper out and I can just grab them, to collate them in order. Eg. Page 100(99) on top shelf, then Page 98(97) in the next slot, then...