You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(4-acetylphenyl)-3-[(2-ethyl-3-oxo-4H-1,4-benzothiazin-6-yl)sulfonyl]propanamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H22N2O5S2
assistant