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:
the usl w-league is a national women's soccer league.

Ex Output:
w-league


Ex Input:
dennis kearney (1847–1907) was an american politician who was himself an immigrant from ireland.

Ex Output:
dennis kearney


Ex Input:
the list of world heritage sites in bulgaria is a group of places chosen by unesco, the united nations educational, scientific and cultural organization.

Ex Output:

list of world heritage sites in bulgaria