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]
}