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: Mark had always wanted to have a pet. Sentence2: He decides to buy a pet cat. Sentence3: Mark loves his new cat. Sentence4: He feels less lonely now that he has a cat. Sentence5: He is glad that he got a pet.
Pet, Pet cat, Mark