You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(5-chloropyridin-2-yl)-2-[(2-methoxyphenyl)methyl-(thiophen-2-ylmethyl)amino]acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H20ClN3O2S
assistant