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: Laura's cat had run away from home. Sentence2: Laura chased her cat to a tree. Sentence3: Laura's cat meowed because it was unable to get down. Sentence4: Laura called the fire department. Sentence5: A friendly firefighter was able to bring her cat out of the tree.
Output:
Laura, Firefighter, Cat