On a large wooden block, there are four twelve-hour analog clocks of varying accuracy. At 7 PM on April 3, 2015, they all correctly displayed the time. The first clock is accurate, the second clock is two times as fast as the first clock, the third clock is three times as fast as the first clock, and the last clock doesn't move at all. How many hours must elapse (from 7 PM) before the times displayed on the clocks coincide again? (The clocks do not distinguish between AM and PM.)

Let's think step by step and output the final answer within \boxed{}.
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