You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4R)-4-(4-fluorophenyl)-1-methyl-6-[[(2S)-oxolan-2-yl]methyl]-4,7-dihydro-3H-pyrrolo[3,4-d]pyrimidine-2,5-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20FN3O3
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