Definition: 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: Willie and Amy decided to pretend to be ducks. Sentence2: They put on yellow shirts and started waddling around. Sentence3: Only they realized they needed bills to really look like ducks. Sentence4: They painted some paper plates yellow. Sentence5: They attached them to their faces with some string and they had bills!
Output:
Amy, Willie