Task: Question Understanding
Input (English): Context : The A.V. Club gave the episode an A, writing ``But ''Fifteen Million Merits`` is a grander work in every way to ''The National Anthem``, a dazzling piece of science fiction that builds its world out slowly but perfectly over the course of an hour--and packs an emotional wallop along with the ''15 minutes into the future`` warning you already expect. 
Question : Which series was Fifteen Million Merits in?
Output (English): series