You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule N'-[3-[(4-oxo-5,6,7,8-tetrahydro-3H-phthalazin-1-yl)methyl]phenyl]-N-phenylpentanediamide into molecular formula.
user
C26H28N4O3
assistant