You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule 2-[(2S,5R)-5-(acetamidomethyl)-1-methylpyrrolidin-2-yl]-N-[2-(4,5-dimethyl-1H-benzimidazol-2-yl)ethyl]acetamide into molecular formula.
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C21H31N5O2
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