Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

Input: Consider Input: a mathematician's apology is a book about mathematics which was written in 1940.

Output: a mathematician's apology

Input: Consider Input: lactarius torminosus, commonly known as the woolly milkcap or the bearded milkcap, is a mushroom in the genus "lactarius".

Output: lactarius torminosus

Input: Consider Input: the features of a production vehicle or production car are mass-produced identical models, offered for sale to the public.
Output: production vehicle