You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-[[6-(ethylamino)-8-(2-hydroxypropan-2-yl)-7H-purin-3-ium-3-yl]methyl]-2-methoxyphenol is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H24N5O3+
assistant