You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4S)-3-(2-hydroxyphenyl)-4-(3-hydroxyphenyl)-5-(3-methoxypropyl)-1,4-dihydropyrrolo[3,4-c]pyrazol-6-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H21N3O4
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