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-(1,3-dimethylpyrazol-4-yl)-1-[(5S)-5-methyl-3-(2-phenylethyl)-6,8-dihydro-5H-[1,2,4]triazolo[4,3-a]pyrazin-7-yl]ethanone is given. What is its corresponding molecular formula?
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C21H26N6O
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