You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1S,2R,3S,5R)-3-[4-(6-aminopyridin-2-yl)butyl]-5-(4-aminopyrrolo[2,3-d]pyrimidin-7-yl)-3-methylcyclopentane-1,2-diol is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H28N6O2
assistant