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.

Sentence1: Dean's teacher began grading him on behavior weekly. Sentence2: Dean promptly dropped the behavioral grading slips in the garbage. Sentence3: Dean's parents never saw them. Sentence4: Dean's parents were asked about them at a parent-teacher conference. Sentence5: When Dean's parents got home, they were livid with Dean.
Dean's parents, Dean, Dean's teacher