You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 2-[2-[[2-(3-cyanopyrrolo[1,2-b]pyridazin-7-yl)-5-[[(2R)-2-fluoro-3-hydroxy-3-methylbutyl]carbamoyl]pyridin-4-yl]amino]spiro[3.3]heptan-6-yl]acetate is the IUPAC name of a molecule. Please give its molecular formula.
user
C87H99F3N18O12
assistant