You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Name the molecular formula for the molecule established as 3-methyl-12-phenyl-3,4,5,12-tetrahydro-2H-benzimidazolo[2,1-b]quinazolin-1-one using the IUPAC nomenclature.
user
C21H19N3O
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