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-(2,3-dihydroindol-1-yl)-2-oxoethyl]-1-ethyl-3-(2-pyridin-2-ylethyl)guanidine is given. What is its corresponding molecular formula?
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C20H25N5O
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