You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 5-[[2-(4-chlorophenyl)benzimidazol-1-yl]methyl]-N-ethyl-1,3,4-thiadiazol-2-amine by IUPAC nomenclature, provide its molecular formula.
user
C18H16ClN5S
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