You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5S,7R)-5-(2,4-dichlorophenyl)-7-naphthalen-1-yl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H16Cl2N4
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