You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance 2-[2-[[2-[(2-amino-3-sulfanylpropanoyl)amino]-3-phenylpropanoyl]amino]propanoylamino]pentanedioic acid .
user
C20H28N4O7S
assistant