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:
mohamed allalou (born september 28, 1973) is an algerian boxer.

Ex Output:
mohamed allalou


Ex Input:
doriva (born 28 may 1972) is a former brazilian football player.

Ex Output:
doriva


Ex Input:
an era in geology is a time of several hundred million years.

Ex Output:

era