You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by (8S)-9-[2-[4-(difluoromethoxy)phenyl]-2-oxoethyl]-2-[(1R,4S)-2-oxa-5-azabicyclo[2.2.1]heptan-5-yl]-8-(trifluoromethyl)-7,8-dihydro-6H-pyrimido[1,2-a]pyrimidin-4-one ?
user
C22H21F5N4O4
assistant