You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(8-tert-butyl-6-methyl-1,4-dioxaspiro[4.5]decan-3-yl)methyl]-N-ethylbutan-1-amine is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H39NO2
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