You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name 1'-[6-methoxy-5-[(E)-1-(2-methylidenehydrazinyl)prop-1-en-2-yl]pyridin-2-yl]spiro[1,3-dihydroindole-2,3'-pyrrolidine]-2'-one into its molecular formula.
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C21H23N5O2
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