You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(6-acetamido-1,3-benzothiazol-2-yl)carbamothioyl]-5-(3,4-dichlorophenyl)furan-2-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H14Cl2N4O3S2
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