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.
Q: Sentence1: Martin was walking home from school. Sentence2: He saw a kid riding his bike. Sentence3: Martin yelled at the kid. Sentence4: The kid took off on his bike. Sentence5: Martin chased him down and beat him up.
A:
Kid, Martin