You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-(1,4-dimethyl-2,3-dioxoquinoxalin-6-yl)sulfonyl-N-(3-ethylphenyl)propanamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H23N3O5S
assistant