You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-(2-chloroethyl)-1-[[(2R,3S,5R)-3-hydroxy-5-(5-methyl-2,4-dioxopyrimidin-1-yl)oxolan-2-yl]methyl]-1-nitrosourea is the IUPAC name of a molecule. Please give its molecular formula.
user
C13H18ClN5O6
assistant