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: Carla's old Doctor switched practices and she needed to get a new one. Sentence2: She was therefore scheduled with dr Pratt. Sentence3: Carla walked into the doctor's office. Sentence4: To her surprise Dr Pratt was very gracious. Sentence5: She liked her a lot.
Dr pratt, Carla, Doctor