You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 1-[1-(3,4-diethoxyphenyl)ethyl]-3-ethyl-2-[3-(3-methyl-1,2,4-oxadiazol-5-yl)propyl]guanidine by IUPAC nomenclature, provide its molecular formula.
user
C21H33N5O3
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