Given a disfluent sentence, modify the sentence to it to its equivalent fluent form, preserving the meaning of the sentence.

Example input: Who did the Han Chinese want to help the Khitan no I mean the Mongols fight?
Example output: Who did the Han Chinese want to help the Mongols fight?
Example explanation: The input initially means Khitan and then changes to Mongols, hence this is correct.
Q: What year did building activity occur on St. Kazimierz Church?
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
When did building activity occur on St. Kazimierz Church?