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: Dan dreaded doing back to school shopping with his kids. Sentence2: However, Dan had to purchase new backpacks and shoes for the kids. Sentence3: Dan decided to go to the mall to get the school shopping done. Sentence4: After looking through several stores, Dan didn't find anything. Sentence5: Dan was disappointed that he did not find anything at the mall.
Example Output: Kids, Dan

Example Input: Sentence1: Paul had a problem with drugs. Sentence2: His Father was very concerned for him. Sentence3: He put him in a rehab center to get help. Sentence4: Paul stayed there for sixty days. Sentence5: He learned how bad drugs really were and never did them again.
Example Output: Paul, Father

Example 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.
Example Output:
Jack, Jack's dad