You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 2-(2-methyl-1H-indol-3-yl)-1-[2-([1,2,4]triazolo[4,3-a]pyridin-3-yl)pyrrolidin-1-yl]ethanone is given. What is its corresponding molecular formula?
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C21H21N5O
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