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 N-[(5-cyclobutyl-1,2,4-oxadiazol-3-yl)methyl]-N-ethyl-2-(3-oxopyrido[3,2-b][1,4]oxazin-4-yl)acetamide ?
user
C18H21N5O4
assistant