You are given a sentence and a question in the input. The information provided in the sentence should be enough to answer the question. You're expected to write the correct answer. Do not use any facts other than those provided in the sentence.

Sentence: The urban area of the Kathmandu valley is split among three different districts (collections of local government units within a zone) which extend very little beyond the valley fringe, except towards the southern ranges, which have comparatively small population. 
Question: How many districts make up the Kathmandu Valley urban area?
three districts.