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- 07:42, 23 August 2011 (diff | hist) . . (+911) . . N AoPS Wiki talk:Problem of the Day/August 23, 2011 (Created page with "Twenty bored students take turns walking down a hall that contains a row of closed lockers, numbered <math>1</math> to <math>20</math>. The first student opens all the lockers; t...")
