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:
lee soo-young (born lee ji-yeon april 12, 1979) is a korean ballad singer.

Ex Output:
lee soo-young


Ex Input:
teleportation is the supposed movement of matter from one point to another without travelling across the physical space between them.

Ex Output:
teleportation


Ex Input:
the gordian knot is a legend of associated with alexander the great.

Ex Output:

gordian knot