You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule N-[1-(2-methoxyphenyl)ethyl]-N-methyl-4-oxo-3,5-dihydro-2H-1,5-benzothiazepine-7-carboxamide into molecular formula.
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C20H22N2O3S
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