You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
8,8-difluoro-2-[(2-methylpropan-2-yl)oxycarbonyl]-2-azaspiro[4.5]decane-4-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H23F2NO4
assistant