You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2,6-difluoro-3-methoxyphenyl)-(1-hydroxy-3-methoxy-7-azaspiro[3.5]nonan-7-yl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C17H21F2NO4
assistant