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: Lucy sat at the police station. Sentence2: She'd been lost and a kind stranger brought her here. Sentence3: She sat with puffy swollen tear stained eyes waiting on her grandpa. Sentence4: An officer gave her a soda while she waited. Sentence5: She was so happy to see grandpa when he arrived, she knocked it over.
Output:
Grandpa, Lucy, Kind stranger, Officer