You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethyl 2-methyl-3-[2-(2-methylpropylamino)-2-oxoethyl]-4-oxo-5,6,7,8-tetrahydro-[1]benzothiolo[2,3-d]pyrimidine-5-carboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H27N3O4S
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