You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (3R)-3-(3-ethylimidazo[4,5-b]pyridin-2-yl)-N-(4-ethylphenyl)pyrrolidine-1-carboxamide into molecular formula.
user
C21H25N5O
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