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.

Input: Consider Input: erzurum is a city in eastern anatolia (asian turkey).

Output: erzurum


Input: Consider Input: nightmare disorder, also known as "dream anxiety disorder", is a sleep disorder characterized by frequent nightmares.

Output: nightmare disorder


Input: Consider Input: wikimania is an international conference on wikis like wikipedia.


Output: wikimania