You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-3-amino-N'-(2-methoxyethyl)-N',2-dimethyl-2-[(2R)-2-methyl-4-phenylbutanoyl]butanediamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H31N3O4
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