You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[2-[4-(azepan-1-ylsulfonyl)piperazin-1-yl]-2-oxoethyl]-6-chloro-4H-1,4-benzothiazin-3-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H27ClN4O4S2
assistant