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.

Example Input: vitoria-gasteiz is the basque country capital.
Example Output: vitoria-gasteiz

Example Input: orathanadu taluk is a taluk of thanjavur district in the indian state of tamil nadu.
Example Output: orathanadu taluk

Example Input: hepatitis b is a disease of the liver.
Example Output:
hepatitis b