In this task, you're given a statement, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.

Context: It is unknown whether his retirement was related to politics. His leaving coincided with the onset of the notorious Second Barons' War in 1264. Link Information: The Second Barons' War (12641267) Question: How many years did the war last that coincided with Bracton's retirement?
Answer: 3