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: Consider Input: Sentence1: Alex owned a lot of money to a loan shark. Sentence2: He was desperate to make money as fast as he could to repay the loan. Sentence3: He went to the casino and gambled everything he had left. Sentence4: In a lucky strike, he quadrupled his earnings. Sentence5: He then paid the loan shark and swore to never borrow money again.

Output: Alex

Input: Consider Input: Sentence1: Tre's bicycle really needed new brakes. Sentence2: Tre saved up all his allowance to take his bike to the shop. Sentence3: On the way a teenager jumped Tre and stole all his money and his bike. Sentence4: Tre walked home crying and empty handed. Sentence5: When he got there he found his mother dead.

Output: A teenager, His mother, Tre

Input: Consider Input: Sentence1: Brandon went to the mailbox. Sentence2: He opened an envelope that reminded him of an overdue book. Sentence3: He immediately drove to the library. Sentence4: The clerk researched his late payment. Sentence5: She said that the system made a mistake since he already gave the book
Output: Clerk, Brandon