Definition: 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: Sentence1: My dad learned how to waterski when he was only four years old. Sentence2: He learned to ski because all of his older brothers skied. Sentence3: He wanted to be just like them. Sentence4: He once entered a skiing contest. Sentence5: He ended up beating his older brothers!
Output:
Dad, Older brothers