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: Greta had brought home all her college textbooks. Sentence2: She stored them in her parents' garage. Sentence3: Years later she finally had her own house. Sentence4: When she went to retrieve them, they all smelled of mildew! Sentence5: Greta was so sad to have to throw out all of her precious books.
Greta, Parents