You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[[4-[4-[(5-chlorothiophen-2-yl)methyl]-5-ethyl-1,2,4-triazol-3-yl]piperazin-1-yl]methyl]benzonitrile The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H23ClN6S
assistant