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: Tim was going to drive a friend home. Sentence2: The friend had too much to drink. Sentence3: He couldn't get the friend's keys to work. Sentence4: The friend was too drunk to help. Sentence5: He had taken the wrong keys by accident.

Ex Output:
Tim, Friend

Ex Input:
Sentence1: Jake wanted to join little league. Sentence2: He had asthma and his parents were worried. Sentence3: He convinced them to let him. Sentence4: He had a lot of fun. Sentence5: His parents decided to trust him more.

Ex Output:
His parents, Jake

Ex Input:
Sentence1: Jake was at the airport. Sentence2: He was running late for his flight. Sentence3: Jake was randomly screened during the security checkpoint. Sentence4: He ended up missing his flight. Sentence5: Jake complained to the security office but they ignored him.

Ex Output:
Security office, Security, Jake