You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (3S)-3-methyl-1-N-(3-methylbutyl)-3-N-[(2-methylphenyl)methyl]piperidine-1,3-dicarboxamide by IUPAC nomenclature, provide its molecular formula.
user
C21H33N3O2
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