You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[(2R,3R,4S,5R)-5-[[[[(2R,3R,4R,5R)-5-(6-aminopurin-9-yl)-3-hydroxy-4-phosphonooxyoxolan-2-yl]methoxy-hydroxyphosphoryl]oxy-hydroxyphosphoryl]-hydroxymethyl]-3,4-dihydroxyoxolan-2-yl]pyridin-1-ium-3-sulfonic acid by IUPAC nomenclature, provide its molecular formula.
user
C20H28N6O19P3S+
assistant