You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 2-chloro-4-[4-(3-piperazin-1-yl-1,2,4-oxadiazol-5-yl)phenyl]benzoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H19ClN4O3
assistant