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:
patau syndrome affects about one in 25,000 live births.

Ex Output:
patau syndrome


Ex Input:
a marriage proposal is when one person in a relationship asks the other person to marry them.

Ex Output:
marriage proposal


Ex Input:
a browser game is a video game that is played on a web browser.

Ex Output:

browser game