You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1S)-1-[(5-methyl-4-nitro-1H-pyrazol-3-yl)methyl]-2-phenyl-3,4-dihydro-1H-isoquinoline is the IUPAC name of a molecule. Please give its molecular formula.
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C20H20N4O2
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