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: Dan wanted to get some exercise in today. Sentence2: Dan decided he would go to the local pool and swim several laps. Sentence3: However, when Dan arrived he noticed the facility was closed. Sentence4: Dan decided he would go back home and exercise there. Sentence5: Dan was disappointed that he could not swim in the pool.

Output: Dan

Input: Consider Input: Sentence1: Tommy has a red balloon. Sentence2: It's his favorite color! Sentence3: But one day, the balloon lost it's air. Sentence4: Tommy was very sad. Sentence5: But he'll get a new balloon tomorrow, so it's not that bad.

Output: Tommy

Input: Consider Input: Sentence1: Jim had lost his cellphone. Sentence2: He searched for hours every where. Sentence3: He decided to call his school. Sentence4: The secretary looked in the lost in found at his school. Sentence5: She found the exact phone he was looking for.
Output: Jim, Secretary