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 1-ethyl-2-[(5-ethyl-1,3-thiazol-2-yl)methyl]-3-(2-phenyl-2-pyrrolidin-1-ylethyl)guanidine .
user
C21H31N5S
assistant