You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(3-chloro-2-methylphenyl)-N-[2-oxo-2-(4-pyridin-2-ylpiperazin-1-yl)ethyl]acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H23ClN4O2
assistant