You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(2-chlorophenyl)-2-[4-[5-(4-fluorophenyl)thiophene-2-carbonyl]piperazin-1-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C23H21ClFN3O2S
assistant