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 group of his hostages nicknamed him "jihadi john" since he was part of a four-person terrorist cell with british accents whom they called "the beatles".

Ex Output:
jihadi john


Ex Input:
filisur is a former municipality of the district albula in the canton of graubünden in switzerland.

Ex Output:
filisur


Ex Input:
kallang mrt station (ew10) is an above-ground mass rapid transit station on the east west line in kallang, singapore.

Ex Output:

kallang mrt station