instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
The Church of the Savior on Spilled Blood, built on the site of the assassination of Tsar Alexander II, is in which Russian city?
answer:
church of the savior on blood


question:
What is the main river of Brazil?
answer:
brazil


question:
What was Barbara Windsor's first Carry On film?
answer:

carry on