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: John really wanted to learn the Russian language. Sentence2: John bought materials and began studying. Sentence3: John watched Russian movies without subtitles. Sentence4: John spent a month living in Russia. Sentence5: Now John is fluent in the Russian language.
Output:
John