Definition: 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: Bob bought a tractor one day. Sentence2: He used it for pulling logs back to his farm house. Sentence3: Bob would then cut the wood and sell it. Sentence4: He made enough money to pay for the tractor. Sentence5: Bob is glad he purchased the tractor.
Output:
Bob