You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
17-isocyano-11-methyl-8,14-dioxo-8,14-diphenyl-1-aza-8lambda5,14lambda5-diphosphapentacyclo[11.7.1.02,7.09,21.015,20]henicosa-2(7),3,5,9(21),10,12,15(20),16,18-nonaene-5-carbonitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C33H21N3O2P2
assistant