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 (7E)-3-(4-fluorophenyl)-7-[(4-fluorophenyl)methylidene]-3a,4,5,6-tetrahydro-3H-indazole-2-carboxamide .
user
C21H19F2N3O
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