You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named tert-butyl N-[2-[1-(6-carbamoyl-2-ethylthieno[3,2-d]pyrimidin-4-yl)piperidin-4-yl]ethyl]carbamate is given. What is its corresponding molecular formula?
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C21H31N5O3S
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