Twenty-Five Swimmers, Five Lanes

A swim coach must identify her three fastest athletes out of 25 25 , but the pool has only 5 5 lanes and the stopwatch is broken — each heat of 5 5 swimmers reveals only their finishing order, never times. Every swimmer performs identically in every heat. What is the minimum number of heats guaranteed to determine the fastest, second-fastest, and third-fastest swimmers?

Answer

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