You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(5-chlorothiophen-2-yl)-4-[4-(2,3-dimethylphenyl)piperazin-1-yl]butane-1,4-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H23ClN2O2S
assistant