You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-[4-(4-ethylbenzoyl)piperazin-1-yl]sulfonyl-3-methylthiophene-2,4-dicarboxylic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H22N2O7S2
assistant