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 went for a walk outside. Sentence2: About 10 minutes later, it started to rainy. Sentence3: Mike ran for cover to try and stay dry. Sentence4: He found some shelter under a bridge in the park. Sentence5: Once it ended, he resumed his walk under the newly formed rainbow.
Output:
Mike