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.

Example Input: Sentence1: Romeo thought he was the fastest kid at school. Sentence2: Romeo challenged his friend to a race on the track. Sentence3: Both of the racers lined up and prepared to take off! Sentence4: However, Romeo's foot slipped and he ended up tripping himself! Sentence5: He skinned his knee badly and was taken away to the nurse.
Example Output: Racers, Friend, Romeo

Example Input: Sentence1: Marcus was playing his guitar at school. Sentence2: His friend Matthew approached him and asked about the music. Sentence3: Soon they were in a heated conversation about their music tastes. Sentence4: The duo decided that they should collaborate on some music. Sentence5: The resulting album was very popular with all of their friends.
Example Output: Marcus, Their friends, Matthew

Example Input: Sentence1: Jeff was amassing a large book collection in his house. Sentence2: He spent one night organizing all the books he had in his house. Sentence3: There were so many books he had to put them in different rooms. Sentence4: When Jeff was finished organizing, he made a card catalogue for them. Sentence5: Jeff was filled with a great sense of accomplishment from his library.
Example Output:
Jeff