You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 1-[2-(3,3-dimethyl-2-oxo-1H-indol-5-yl)ethyl]-3-(2,2-dimethylpropyl)urea by IUPAC nomenclature, provide its molecular formula.
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C18H27N3O2
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