You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule 3-ethyl-6-hydroxy-2-methylsulfanyl-5-(2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-yl)pyrimidin-4-one into molecular formula.
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C18H20N4O2S
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