Melancholia - Season 1 Episode 1 Fermat’s Last Theorem
Overview: At Asung High, Yoon Su’s new workplace, she gives a tricky question for students who want to join the math club. While no one in the class got the question right, a correct answer sheet is posted on the board outside the classroom. To find out who did it, Yoon Su provokes them and manages to find who it is.