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.
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Question: Sentence1: Zack was always worried about getting sick. Sentence2: And he became so worried about the air that he wore a respirator. Sentence3: He wore it during his entire school day. Sentence4: And he told other students that the air quality was terrible. Sentence5: Zack still ended up getting sick and worried much more.

Answer: Other students, Zack

Question: Sentence1: Ken is a DJ for a club. Sentence2: Last night he had a really annoying patron. Sentence3: They kept asking for different songs. Sentence4: Ken kept having to turn him down. Sentence5: Eventually he just ignored him completely.

Answer: Ken, Annoying patron

Question: Sentence1: Sam was on a field trip. Sentence2: They were at the zoo. Sentence3: The teacher said to stay with the group. Sentence4: Sam didn't listen and got lost. Sentence5: However, by the end of the day he found the class.

Answer:
The teacher, Sam