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 (3S)-3-methyl-1-[(4-methylphenyl)methyl]-4-(2-methyl-5-propan-2-ylpyrazole-3-carbonyl)piperazin-2-one into molecular formula.
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C21H28N4O2
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