You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 3-ethyl-6-[(3R)-3-(5,6,7,8-tetrahydroquinazolin-4-ylamino)pyrrolidin-1-yl]-1H-pyrimidine-2,4-dione by IUPAC nomenclature, provide its molecular formula.
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C18H24N6O2
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