After complaints from the residents of Tatoosh about the number of cats on the island, the wildlife service carried out a relocation mission that saw the number of cats on the island drastically reduced. On the first relocation mission, 600 cats were relocated from the island to a neighboring island. On the second mission, half of the remaining cats were relocated to a rescue center inland. If the number of cats originally on the island was 1800, how many cats remained on the island after the rescue mission?
Please reason step by step, and put your final answer within \boxed{}.
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