Given the task definition and input, reply with output. 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: Brandon went to the mailbox. Sentence2: He opened an envelope that reminded him of an overdue book. Sentence3: He immediately drove to the library. Sentence4: The clerk researched his late payment. Sentence5: She said that the system made a mistake since he already gave the book

Clerk, Brandon