You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(5R,6R)-6-fluoro-9-(5-methylpyrimidin-2-yl)-2,9-diazaspiro[4.5]decan-2-yl]-(furan-2-yl)methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H21FN4O2
assistant