Santa's exam

Santa is in his final examination that consists of "yes/no" type questions. He takes his seat in the examination hall, stares at the question paper for five minutes, and then in a fit of inspiration takes a coin out from his pocket and starts tossing the coin and marking the answer sheet Yes for Heads and No for Tails. Within half an hour he is all done whereas the rest of the class is still sweating it out. During the last few minutes,he is seen desperately throwing the coin, muttering and sweating.
The teacher, alarmed, approaches him and asks what is going on.
"I finished the exam in half an hour," he explained, "but now I'm rechecking my answers."

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