You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-(2-tert-butylsulfonylethyl)-3-ethyl-2-[2-(4-fluorophenyl)-2-morpholin-4-ylethyl]guanidine by IUPAC nomenclature, provide its molecular formula.
user
C21H35FN4O3S
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