digraph g { "a1" -> "a2" [label="O",arrowhead=normal] "a2" -> "a3" [label="O",arrowhead=normal] "a3" -> "a4" [label="O",arrowhead=normal] "a4" -> "a5" [label="O",arrowhead=normal] "a5" -> "a6" [label="O",arrowhead=normal] "a6" -> "a7" [label="O",arrowhead=normal] "a7" -> "a8" [label="O",arrowhead=normal] "a8" -> "a9" [label="O",arrowhead=normal] "a9" -> "a10" [label="O",arrowhead=normal] "a10" -> "a1" [label="O",arrowhead=normal] "a10" -> "b1" [label="O",arrowhead=normal] "b1" -> "b2" [label="O",arrowhead=normal] "b2" -> "b3" [label="O",arrowhead=normal] "b3" -> "b4" [label="O",arrowhead=normal] "b4" -> "b5" [label="O",arrowhead=normal] "b5" -> "b6" [label="O",arrowhead=normal] "b6" -> "b7" [label="O",arrowhead=normal] "b7" -> "b1" [label="O",arrowhead=normal] }