You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by 3-[(1R)-2-(7-ethyl-1H-indol-3-yl)-2-oxo-1-phenylethyl]-4-oxophthalazine-1-carboxylic acid ?
user
C27H21N3O4
assistant