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.

Ex Input:
Sentence1: David was whistling in class. Sentence2: The teacher didn't know who was making the noise. Sentence3: She didn't know who to punish. Sentence4: One of the students told the teacher after class that it was David. Sentence5: The next time David whistled, the teacher blamed David.

Ex Output:
One of the students, Teacher, David

Ex Input:
Sentence1: Scot was a tiny puppy who loved to bark at things. Sentence2: She loved to bark at the springy doorstop most of all. Sentence3: She would thwack it with her nose and bark, bark, bark all day. Sentence4: Her people decided to remove the doorstop to get some peace and quiet. Sentence5: Scout didn't mind - she just barked at the wall instead!

Ex Output:
Her people, Scot

Ex Input:
Sentence1: Charles learned to be creative from his grandmother. Sentence2: One thanksgiving, she asked him to cut up a watermelon. Sentence3: Charles cut up a bunch of chunks and put them in Tupperware. Sentence4: His grandmother told him to be more creative. Sentence5: Then she carved a basket out of a watermelon and put the chunks in.

Ex Output:
Grandmother, Charles