You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[4-(5-methyl-1H-1,2,4-triazol-3-yl)phenyl]-4-oxo-4-(3-oxo-2,4-dihydroquinoxalin-1-yl)butanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20N6O3
assistant