You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[3-benzyl-7-(2-methoxyethyl)-2,6-dioxo-9H-purin-7-ium-1-yl]acetic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C17H19N4O5+
assistant