You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (4S)-3'-[[3-(3-methoxyphenyl)-1,2,4-oxadiazol-5-yl]methyl]spiro[6,7-dihydro-5H-1-benzothiophene-4,5'-imidazolidine]-2',4'-dione into molecular formula.
user
C20H18N4O4S
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