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:
henry's marriage to catherine of aragon was finally annulled in the following may by archbishop cranmer, thus ending the first of henry's 6 marriages.

Ex Output:
catherine of aragon


Ex Input:
louise leakey (born 21 march 1972) is a kenyan paleontologist.

Ex Output:
louise leakey


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

Ex Output:

corruption perceptions index