You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[3-[(5-bromo-6-methoxypyridin-2-yl)amino]sulfanyl-6-chloroindol-1-yl]ethanol;ethane is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21BrClN3O2S
assistant