You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5S,7R)-5-(2-chlorophenyl)-7-(3-methoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-amine The above is the IUPAC name of a molecule. Write its molecular formula.
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C18H18ClN5O
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