You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-ethyl-2-[2-(3-methoxyphenoxy)ethyl]-3-(1-thiophen-2-ylpiperidin-4-yl)guanidine by IUPAC nomenclature, provide its molecular formula.
user
C21H30N4O2S
assistant