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: Will was moved up a grade because he was so smart. Sentence2: The teachers warned his dad that he wouldn't grow emotionally. Sentence3: His dad insisted on moving him up a grade. Sentence4: Will was hated throughout school. Sentence5: He is now a very confused and disliked adult.
Example Output: Will, Dad, School, Teachers

Example Input: Sentence1: Yusuf was startled by a loud knocking at his door at a late hour. Sentence2: He wasn't expecting company, and grabbed his gun. Sentence3: A shivering woman greeted him when he opened the door. Sentence4: She had hit black ice and her car had slid off the road. Sentence5: Yusuf called a tow truck for her, and let her warm up in his house.
Example Output: Yusuf, Woman

Example Input: Sentence1: Helen needed a haircut. Sentence2: She went to the beauty salon. Sentence3: It was crowded with customers. Sentence4: Helen waited a long time in the salon. Sentence5: Finally, she got the haircut that she wanted.
Example Output:
Crowd, Helen