You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-[(3R,3aR)-3-(hydroxymethyl)-1-oxo-3a,4-dihydro-3H-[1,3]oxazolo[3,4-a]indol-6-yl]-N-methylpyridine-2-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H17N3O4
assistant