You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-(1-methylselanylpropyl)-1-phenyl-3,3-bis(trifluoromethyl)-2,1-benzoxaphosphol-1-ium The above is the IUPAC name of a molecule. Write its molecular formula.
user
C19H18F6OPSe+
assistant