You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[1-(2-ethyl-1,2,4-triazol-3-yl)ethyl]-5-phenyl-6,7-dihydropyrrolo[3,2-d]pyrimidin-2-amine The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H21N7
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