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: Sam was changing the light bulb. Sentence2: He screwed in the new light bulb. Sentence3: He felt a shock on his hand. Sentence4: He had been electrocuted! Sentence5: Fortunately, Sam was not injured by this incident.
Sam