Definition: In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.
Input: Sentence1: Don showed up for his clarinet lesson. Sentence2: He forgot to bring his music. Sentence3: A teacher told him to play some scales. Sentence4: Don really was not ready for that. Sentence5: After that they played some duets with teacher.
Output:
Don, Teacher