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: 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.
Example Output: Bret

Example Input: Sentence1: Rick was at a restaurant. Sentence2: And he was curious about how all of the different items tasted. Sentence3: So he ordered way more than he could eat. Sentence4: And he forced himself to finish everything out of guilt. Sentence5: Rick tried to quell his curiosity the next time.
Example Output: Rick

Example Input: Sentence1: Abby's sister had recently gone into labor. Sentence2: Abby was excited, yet nervous to be in the delivery room with her. Sentence3: As time came to push, Abby got to see the beauty of birth. Sentence4: Abby began crying at the great miracle that she witnessed. Sentence5: Abby was glad to be there to see her nephew's Birthday.
Example Output:
Abby's sister, Abby