You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(1-methylazet-1-ium-3-yl)amino]ethenyl-[1-[3-(phenylcarbamoylamino)phenyl]ethyl]azanide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23N5O
assistant