You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance [(3S)-5-(4-chlorophenyl)-3-(2-hydroxyphenyl)-3,4-dihydropyrazol-2-yl]-(1-ethyl-4-nitropyrazol-3-yl)methanone .
user
C21H18ClN5O4
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