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: Bret went mountain climbing in Alaska. Sentence2: He was near the summit of the mountain when a storm struck. Sentence3: Bret had to build a snow cave to keep warm. Sentence4: Bret survived the storm that lasted two days. Sentence5: Bret was glad that he knew mountain survival techniques.

Ex Output:
Bret

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: Lillian had always been rich. Sentence2: She went from her rich family to a rich husband. Sentence3: Now that she was divorced and penniless, she was dismayed. Sentence4: She had to find a job and work for the first time of her life. Sentence5: But after a few years, she was proud of herself, and doing well.

Ex Output:
Lillian, Husband, Family