You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
6-chloro-N,3-diphenyl-4-pyridin-4-yl-7-(2,4,6-trichlorophenyl)-1,3,5-thiadiazepin-2-imine is the IUPAC name of a molecule. Please give its molecular formula.
user
C27H16Cl4N4S
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