You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule N-(3,4-dichlorophenyl)-2-[(4-oxo-5-phenyl-3H-thieno[2,3-d]pyrimidin-2-yl)methylsulfanyl]acetamide ?
user
C21H15Cl2N3O2S2
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