You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (3R)-3-amino-N-[(2R)-3-(4-chlorophenyl)-1-(methylamino)-1-oxopropan-2-yl]-4-(2-fluorophenyl)butanamide .
user
C20H23ClFN3O2
assistant