Instructions: 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: 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