An orchard has 1200 apple trees. During the harvesting season, 3/8 of the trees are harvested in the first week. In the second week, 50% of the remaining trees are harvested. In the third week, 1/3 of the trees that were harvested in the second week are harvested again due to an error in counting. How many trees were left unharvested by the end of the third week? Let's think step by step and output the final answer within \boxed{}.
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