You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-deuterio-9-[2-(2,5-difluorophenyl)ethyl]-4-ethyl-2-methyl-1-oxa-4,9-diazaspiro[5.5]undecan-3-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H26F2N2O2
assistant