You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-[2-cyclohexyl-2-(dimethylamino)ethyl]-1-ethyl-3-[3-(2-oxopyrrolidin-1-yl)propyl]guanidine by IUPAC nomenclature, provide its molecular formula.
user
C20H39N5O
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