Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

Example Input: Which SF author wrote The Day it Rained Forever?
Example Output: the day it rained forever

Example Input: Which legal drama starring Martin Shaw ran for six series on BBC TV from 2001?
Example Output: martin shaw

Example Input: BCG vaccine is used against which infectious disease?
Example Output:
bcg vaccine