You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(4-ethoxyphenyl)-5-[(3-methyl-1,2,4-oxadiazol-5-yl)methyl]pyrazolo[1,5-a]pyrazin-4-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H17N5O3
assistant