You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[9-[(1S,3S,4R,7S)-1-ethyl-7-hydroxy-2,5-dioxabicyclo[2.2.1]heptan-3-yl]purin-6-yl]benzamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H19N5O4
assistant