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 (6R)-8-(2-ethylpyrazole-3-carbonyl)-2-(pyridin-4-ylmethyl)-2,8-diazaspiro[5.5]undecan-3-one into molecular formula.
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C21H27N5O2
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