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: pablo escobar and his brother's school once sent them home because they had no shoes and no money to buy them.
Example Output: pablo escobar

Example Input: the boeing monomail was a monoplane instead of a biplane.
Example Output: boeing monomail

Example Input: the cessna 188 is a single-engine agricultural aircraft.
Example Output:
cessna 188