Q: In this task, you're given passages that contain mentions of the quantity of a particular object and are supposed to find out the answer for a given question. Craft one correct answer to the question given in input. Make sure your correct answer is consistent with the context, and properly gives the exact number relating to the query.
 In your answer, use as few words as possible from the given context. To be less repetitive, please vary your language for each question.
Sentence: The 21 nocturnes are more structured, and of greater emotional depth, than those of Field (whom Chopin met in 1833). Many of the Chopin nocturnes have middle sections marked by agitated expression (and often making very difficult demands on the performer) which heightens their dramatic character. 
Question: How many nocturnes did Chopin compose?
A:
21