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.

Ex Input:
Sentence1: Ken was a cook. Sentence2: Ken was given an order for a medium rare steak. Sentence3: Ken cooked up the steak nice and rare. Sentence4: He went to serve it to the customers. Sentence5: The customer told him they wanted it well done.

Ex Output:
Customer, Ken, Customers

Ex Input:
Sentence1: Jim was sitting alone in his room, bored. Sentence2: He decided to go out and do something. Sentence3: He tagged the stop sign at the end of his street. Sentence4: A cop sat in his cruiser and watched him do it. Sentence5: Jim got sentenced to six months in juvenile detention.

Ex Output:
Cop, Jim

Ex Input:
Sentence1: Charles wanted a raise. Sentence2: He was nervous about asking his boss. Sentence3: He finally built up enough courage to do it. Sentence4: His boss appreciated his initiative. Sentence5: Charles got a raise.

Ex Output:
Charles, Boss