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.

Ex Input:
fair use is the idea that it should be okay for a person to reuse something that another person has created, in certain amounts and for certain purposes, without breaking the law.

Ex Output:
fair use

Ex Input:
the corruption perceptions index is an index that shows how corrupt certain countries are.

Ex Output:
corruption perceptions index

Ex Input:
the mongolian language (, "mongol kele", cyrillic: , "mongol khel") is the best-known member of the mongolic language family and the language of most of the residents of mongolia, where it is officially written with the cyrillic alphabet and of around three million mongolian speakers in the "inner mongolia autonomous region" of china, where it is officially written with the traditional mongolian script.

Ex Output:
mongolian language