You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[2-[(2S)-2-methyl-3,4-dihydro-2H-1,5-benzothiazepin-5-yl]-2-oxoethyl] 4-carbamoylbenzoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20N2O4S
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