You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(Z)-4-[5-(1-benzothiophen-2-ylmethyl)thiophen-2-yl]but-3-en-2-yl]-1-hydroxyurea is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H18N2O2S2
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