You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (8S)-2-[[(2S,5R)-3-oxabicyclo[3.1.0]hexan-2-yl]methylamino]-9-[2-(oxan-4-yl)-2-oxoethyl]-8-(trifluoromethyl)-7,8-dihydro-6H-pyrimido[1,2-a]pyrimidin-4-one by IUPAC nomenclature, provide its molecular formula.
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C21H27F3N4O4
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