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.

Example Input: a modest proposal is a famous work of satire by irish writer jonathan swift.
Example Output: a modest proposal

Example Input: love hina is a japanese manga.
Example Output: love hina

Example Input: a floor is a horizontal surface inside a building.
Example Output:
floor