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: I made myself a tuna sandwich for lunch. Sentence2: As I was sitting down to eat, the phone rang. Sentence3: I got up to answer the phone and had a short conversation. Sentence4: When I returned, my sandwich was gone and my dog was looking happy. Sentence5: I will never trust a sandwich alone in my house again.
Output:
I (myself), Dog