You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (2S)-2-[(6-methoxy-1H-benzimidazol-2-yl)sulfanyl]-1-(4-methoxyphenyl)propan-1-one by IUPAC nomenclature, provide its molecular formula.
user
C18H18N2O3S
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