You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
azepan-1-yl-[1-[(3-phenyl-1,2,4-oxadiazol-5-yl)methyl]piperidin-3-yl]methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H28N4O2
assistant