You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (1R,2R)-2-N-[(2S)-2-amino-3-phenylpropyl]-1-N,1-N,2-N-trimethylcyclohexane-1,2-diamine into molecular formula.
user
C18H31N3
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