digraph g { "a" -> "d" [label="op",arrowhead=normal] "a" -> "e" [label="op",arrowhead=normal] "a" -> "f" [label="op",arrowhead=normal] "b" -> "d" [label="op",arrowhead=normal] "b" -> "e" [label="op",arrowhead=normal] "b" -> "f" [label="op",arrowhead=normal] "c" -> "d" [label="op",arrowhead=normal] "c" -> "e" [label="op",arrowhead=normal] "c" -> "f" [label="op",arrowhead=normal] "d" -> "a" [label="op",arrowhead=normal] "d" -> "b" [label="op",arrowhead=normal] "d" -> "c" [label="op",arrowhead=normal] "e" -> "a" [label="op",arrowhead=normal] "e" -> "b" [label="op",arrowhead=normal] "e" -> "c" [label="op",arrowhead=normal] "f" -> "a" [label="op",arrowhead=normal] "f" -> "b" [label="op",arrowhead=normal] "f" -> "c" [label="op",arrowhead=normal] }