You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[4-[(5-cyclopropyl-1,2,4-oxadiazol-3-yl)methyl]morpholin-3-yl]-1-phenylethanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21N3O3
assistant