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: Mike and Tony bought a baby duck at the spring festival. Sentence2: It was decided that Mike was going to keep the duck at night. Sentence3: Tony came and pick the duck up one morning. Sentence4: He never returned the duck that night. Sentence5: The next day he told Mike that the duck had died.
Output:
Tony, Mike, Duck