You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named N-[4-[2-[4-[(3-chlorophenyl)methyl]piperazin-1-yl]-2-oxoethyl]sulfanylphenyl]acetamide by IUPAC nomenclature, provide its molecular formula.
user
C21H24ClN3O2S
assistant