You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(2-chloro-4-methylphenyl)-4-(6,7-dihydro-4H-thieno[3,2-c]pyridin-5-yl)-4-oxobutanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H19ClN2O2S
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