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.
Q: Sentence1: John did not know how to roller skate. Sentence2: His friend said that he would teach him. Sentence3: They spent all day practicing skating. Sentence4: John kept trying and got very good. Sentence5: Now he roller skates all over the neighborhood.
A:
John, Friend