You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 4-oxo-N-(3,4,5-trimethoxyphenyl)-3,5-dihydro-2H-1,5-benzothiazepine-7-sulfonamide into its molecular formula.
user
C18H20N2O6S2
assistant