You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[4-[4-(3,4-dichlorophenyl)piperazin-1-yl]phthalazin-1-yl]-(4-phenylpiperazin-1-yl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C29H28Cl2N6O
assistant