Instructions: 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: Nora was reading a book. Sentence2: She brought the book with her to the doctor's office. Sentence3: Nora forgot the book at the doctor's office. Sentence4: Nora realized she forgot the book. Sentence5: She went back to the office to retrieve her book.
Output:
Nora