You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (3S)-3-[(4-oxo-3,5-dihydro-2H-1,5-benzothiazepin-7-yl)sulfonyl]-N-phenylbutanamide by IUPAC nomenclature, provide its molecular formula.
user
C19H20N2O4S2
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