You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-ethyl-8-(4-methoxyphenyl)-1-methyl-4a,9a-dihydropurino[8,9-c][1,2,4]triazole-2,4-dione The above is the IUPAC name of a molecule. Write its molecular formula.
user
C16H18N6O3
assistant