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: the corruption perceptions index is an index that shows how corrupt certain countries are.
Example Output: corruption perceptions index

Example Input: the castle of almansa is a castle in almansa, spain.
Example Output: castle of almansa

Example Input: the airbus a380 (also called "super-jumbo-jet") is a four-engined, double-decked airplane manufactured by airbus.
Example Output:
airbus a380