Q: 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.
Sentence1: Martin realizes that he needs to get more exercise. Sentence2: He decides to have a walk around the block before he goes to bed. Sentence3: That night he sleeps more deeply than normal. Sentence4: He decides to take a walk every night before going to bed. Sentence5: Martin is very happy he is getting more exercise.
A:
Martin