You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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N-[(1S)-1-(2,4-dichlorophenyl)ethyl]-3-(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-6-yl)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
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C18H19Cl2N5O
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