You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [2-[butyl-(1,1-dioxothiolan-3-yl)amino]-2-oxoethyl] 4-(4-chlorophenyl)-4-oxobutanoate by IUPAC nomenclature, provide its molecular formula.
user
C20H26ClNO6S
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