You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 2-[[4-amino-5-(2-chlorophenyl)-1,2,4-triazol-3-yl]sulfanylmethyl]-7-methylpyrido[1,2-a]pyrimidin-4-one .
user
C18H15ClN6OS
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