You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(4-fluoro-2,6-dimethylphenyl)-4-[[4-fluoro-2-(trifluoromethyl)phenyl]methyl]piperazine-2,3-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H17F5N2O2
assistant