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: Bob wanted to smoke a cigarette. Sentence2: However, he forgot his lighter. Sentence3: He went to his friend and asked for one. Sentence4: His friend said he doesn't have one. Sentence5: Bob knows his friend has one however.
A:
Bob, Friend