You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4-ethylpiperazin-1-yl)-[1-(4-methoxyphenyl)-3-methyl-5-propan-2-ylpyrazol-4-yl]methanone is the IUPAC name of a molecule. Please give its molecular formula.
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C21H30N4O2
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