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.

Example Input: Sentence1: Zaddy Tracks is a black cat. Sentence2: He is over ten years old. Sentence3: Last spring he got very sick. Sentence4: He went to the veterinarian who gave him some pills for his liver. Sentence5: Zaddy Tracks got better.
Example Output: Zaddy, Veterinarian

Example Input: Sentence1: Matt's mom promised a surprise for him after school. Sentence2: He was excited all day. Sentence3: So excited that he wasn't paying attention during math class. Sentence4: When he didn't answer when called, he was given detention. Sentence5: Matt would have to wait longer to find out what was his surprise.
Example Output: Matt, Matt's mom

Example Input: Sentence1: Mila wanted a pet. Sentence2: She went to the pet store to look for one. Sentence3: At the pet store Mila saw a puppy. Sentence4: Mila loved the puppy and took it home. Sentence5: Mila was happy she found her new pet.
Example Output:
New pet, Puppy, Mila