You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[[(3R)-2,3-dihydro-1,4-benzodioxin-3-yl]methyl]-1-methyl-3-[(1S)-1-pyridin-3-ylethyl]urea The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H21N3O3
assistant