Instructions: 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: Mitch was trying to earn a few extra dollars over the summer. Sentence2: He offered to mow his neighbor's' yards. Sentence3: Four of his neighbors took him up on the offer. Sentence4: Mitch mowed their yards once a week. Sentence5: By the end of the summer, Mitch had saved up a couple hundred dollars.
Output:
Neighbors, Mitch, Four neighbor