You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-[(4-bromophenyl)methyl]-1'-pyridin-4-ylspiro[3,6,8,8a-tetrahydro-[1,3]oxazolo[3,2-a]pyrazine-2,4'-piperidine]-5-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H25BrN4O2
assistant