You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[3-[[(2R,3S,4R,5R)-5-(6-amino-1,2,3,4,5,6,7,8-octahydropurin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl-methylamino]propyl]-3-[2-(thiolan-2-yl)ethyl]urea is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H42N8O4S
assistant