You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (3S)-2-[(2S)-2-methyl-3-oxo-4H-1,4-benzothiazine-6-carbonyl]-3,4-dihydro-1H-isoquinoline-3-carboxylic acid by IUPAC nomenclature, provide its molecular formula.
user
C20H18N2O4S
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