You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
8'-[[(1R)-1-[3-(difluoromethyl)-2-fluorophenyl]ethyl]amino]-1'-methylspiro[cyclopropane-1,3'-pyrrolo[3,2-g]phthalazine]-2'-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H19F3N4O
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