You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance N-(3,4-dimethoxyphenyl)-2-[6-(dimethylsulfamoyl)-2-oxothieno[2,3-b][1,4]thiazin-1-yl]acetamide .
user
C18H21N3O6S3
assistant