You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name [2-(2,2-dimethyl-3-oxo-4H-quinoxalin-1-yl)-2-oxoethyl]-methyl-[(2-methylphenyl)methyl]azanium into its molecular formula.
user
C21H26N3O2+
assistant