You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-[(4-chlorophenyl)methyl-[2-[methyl(methylsulfonyl)amino]acetyl]amino]-N-(2-methylpropyl)propanamide by IUPAC nomenclature, provide its molecular formula.
user
C18H28ClN3O4S
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