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:
a rearguard is a part of a military force that protects the main force from attack from the rear.

Ex Output:
rearguard

Ex Input:
auquainville is a commune.

Ex Output:
auquainville

Ex Input:
area code 701 is an area code for the u.s. state of north dakota.

Ex Output:
area code 701