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.

Input: Consider Input: Sentence1: Galen's father loved sailboats. Sentence2: Galen never had time to learn to sail. Sentence3: One day, he decided that he wanted to try it out. Sentence4: Galen asked his father to teach him to sail. Sentence5: He now has a new favorite hobby.

Output: Galen, Father

Input: Consider 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.

Output: Bret

Input: Consider Input: Sentence1: Tim is an avid coffee drinker. Sentence2: When he woke up this morning, his coffee maker was broken. Sentence3: He remembered he had a starbucks gift card. Sentence4: Tim waited in the drive-thru line for 15 minutes. Sentence5: He did not enjoy the coffee that he had bought.
Output: Tim