Given the task definition and input, reply with output. 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.

Sentence1: Michelle was looking forward to going to prom with her boyfriend Mark. Sentence2: Mark cancelled two hours before prom, he was sick. Sentence3: Michelle did not know what to do. Sentence4: She went anyway. Sentence5: She ended up having a great time, dancing with her friends.
Michelle, Friends, Mark