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: lee bowyer (born 3 january 1977) is an english football player.
Example Output: lee bowyer

Example Input: a marriage proposal is when one person in a relationship asks the other person to marry them.
Example Output: marriage proposal

Example Input: the british rail class 931 was reserved for former southern region electrical multiple units converted for departmental use.
Example Output:
british rail class 931