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: Martha sat quietly on the subway as she waited for her stop. Sentence2: An elderly woman boarded the train and held onto the subway rail. Sentence3: Martha felt bad. Sentence4: She stood up and offered her seat to the elderly woman. Sentence5: The woman thanked Martha enthusiastically.

Output: Woman, Martha, Elderly woman

Input: Consider Input: Sentence1: Warren didn't like beets and told his mom repeatedly. Sentence2: But as she never listened, he had some on his plate for dinner. Sentence3: He tried to give them to his dog. Sentence4: The dog sniffed them and walked away. Sentence5: Warren refused to eat the beets as his dog didn't want them either.

Output: Dog, Mom, Warren

Input: Consider Input: Sentence1: Fred's son had a baseball game today. Sentence2: He promised him he would be there. Sentence3: But at the end of the day Fred never came. Sentence4: His son was so upset and had been looking forward to him. Sentence5: Fred was simply stuck in bad traffic and it was impossible to come.
Output: Fred, Fred's son