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: When Poppy was growing up, she had a very special doll. Sentence2: She took the doll with her everywhere. Sentence3: As she got older, her mother tried to make her give up the doll. Sentence4: Poppy hid the doll so her mother couldn't find it. Sentence5: But Poppy's dog found the doll and chewed it to pieces.
Output:
Poppy, Dog, Mother