You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (2E,4E,6E,8E)-9-(2,6-dichloro-4-methoxy-3-methylphenyl)-N-ethyl-6-fluoro-3,7-dimethylnona-2,4,6,8-tetraenamide .
user
C21H24Cl2FNO2
assistant