You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-hydroxy-3-[1-(2-hydroxyethyl)-2-tridecanoyl-4,5-dihydroimidazol-1-ium-1-yl]propane-1-sulfonic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H41N2O6S+
assistant