You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethyl 2-[3-phenyl-4-(pyridin-2-ylmethylamino)thieno[2,3-b]pyridin-6-yl]acetate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C23H21N3O2S
assistant