You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4aS,8aS)-1-benzyl-2-oxido-2-phenoxy-4a,5,6,7,8,8a-hexahydro-4H-benzo[d][1,3,2]oxazaphosphinin-2-ium is the IUPAC name of a molecule. Please give its molecular formula.
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