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

Let me give you an example: Who did the Han Chinese want to help the Khitan no I mean the Mongols fight?
The answer to this example can be: Who did the Han Chinese want to help the Mongols fight?
Here is why: The input initially means Khitan and then changes to Mongols, hence this is correct.

OK. solve this:
What borders er when did the Peace of Westphalia last until?
Answer:
When did the Peace of Westphalia last until?