You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[[(2R,5R)-5-(6-amino-8-azidopurin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl]isoindole-1,3-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H15N9O5
assistant