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.
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Question: Sentence1: Tom wanted to secure his future. Sentence2: He decided to learn how to program. Sentence3: He google searched for days to determine the best language. Sentence4: He decided that Ruby was the best programming language for him. Sentence5: He bought books on Ruby and worked hard, he learned Ruby well.

Answer: Tom

Question: Sentence1: Greta had noticed her son was having trouble focusing in school. Sentence2: Greta took her son to the doctor. Sentence3: The doctor diagnosed the boy with ADHD. Sentence4: The doctor prescribed medicine for him. Sentence5: Greta's son now focuses much better in class.

Answer: Greta, Greta's son, The doctor

Question: Sentence1: Sean went to a concert. Sentence2: He ran into the restroom between songs. Sentence3: There was a long line to use the restroom. Sentence4: Sean exited the restroom and returned to his seat. Sentence5: He had missed his favorite song.

Answer:
Sean