You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N'-[5-(5,6,7,8-tetrahydronaphthalen-2-yl)thieno[2,3-d]pyrimidin-4-yl]ethane-1,2-diamine is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20N4S
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