You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(3,5-difluorophenyl)methyl]-3-[6-(trifluoromethyl)pyridin-3-yl]-1,3,8-triazaspiro[4.5]decane-2,4-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H17F5N4O2
assistant