You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 2-methylsulfanyl-N-[[(2S)-7-pyrazin-2-yl-2,3-dihydro-1-benzofuran-2-yl]methyl]pyridine-3-carboxamide into molecular formula.
user
C20H18N4O2S
assistant