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: Jack's dad had just bought him a four wheeler. Sentence2: It was Jack's first time riding it and he took a turn too sharp. Sentence3: The ATV tipped and through Jack off of it into a tree. Sentence4: Jack was lucky he was wearing a helmet or he could have been hurt. Sentence5: Jack's dad decided to sell the four wheeler and get Jack an XBox.
Output:
Jack, Jack's dad