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: a diode is an electronic component with two electrodes (connectors) that allows electricity to go through it in one direction and not the other direction.
Example Output: diode

Example Input: saint-paul-de-vence is a commune.
Example Output: saint-paul-de-vence

Example Input: ash ketchum (satoshi in japanese) is a character from the "pokémon" anime.
Example Output:
ash ketchum