You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4S)-4-(4-ethoxyphenyl)-6-(2-methoxyethyl)-1-prop-2-enyl-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
C20H25N3O4
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