You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-(cyclopropylmethyl)-2-[2-(2,3-difluorophenyl)acetyl]-2,7-diazaspiro[4.5]decan-6-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H24F2N2O2
assistant