You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(2,6-dichlorophenoxy)-1-[4-[(4-fluorophenyl)methyl]-2,5-dimethylpiperazin-1-yl]ethanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H23Cl2FN2O2
assistant