You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[4-(1-benzyl-5-chloro-3-methylpyrazole-4-carbonyl)piperazin-1-yl]-(4-ethylphenyl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C25H27ClN4O2
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