You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-ethyl-2-[(5-ethyl-1,3-thiazol-2-yl)methyl]-3-[2-(4-fluorophenoxy)propyl]guanidine by IUPAC nomenclature, provide its molecular formula.
user
C18H25FN4OS
assistant