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: Willie had too much stuff. Sentence2: Willie bought a shed to store all his stuff. Sentence3: Willie had a hard time putting up the shed. Sentence4: He called some friends for help. Sentence5: With the assistance of his friends they finished the shed.
Friends, Willie