You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[4-[(2-chlorophenyl)methyl]piperazin-1-yl]-N-[(Z)-(4-nitrophenyl)methylideneamino]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H22ClN5O3
assistant