You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 4-chloro-5-[4-[[(2S)-oxolan-2-yl]methyl]piperazin-1-yl]-2-[5-(trifluoromethyl)pyridin-2-yl]pyridazin-3-one by IUPAC nomenclature, provide its molecular formula.
user
C19H21ClF3N5O2
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