You will be given a definition of a task first, then some input of the task.
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: One day Penelope found a short story left on her desk in Math class. Sentence2: The next day, there was another story. Sentence3: Every day for two weeks she found a story on her desk. Sentence4: She enjoyed the stories and wondered who wrote them. Sentence5: She was surprised to find that her best friend, John, was the writer.
Output:
Penelope, John