You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[5-[(2,5-dichlorophenyl)methyl]-4,4a,6,7-tetrahydro-1H-pyrazino[2,3-c]pyridazin-3-yl]-5-piperidin-4-yl-1,3,4-oxadiazole is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H23Cl2N7O
assistant