digraph G {
	margin=0;
	nodesep=0.3;
	ranksep=0.3;
	
	{rank=same;
	1 [shape=circle, label="1", fontcolor=blue, group=l];
	2 [shape=circle, label="2", fontcolor=blue, group=r];
	fourd [shape=circle, label="4d", fontcolor=blue, group=3];
	}
	{rank=same;
	threeb [shape=circle, label="3b", fontcolor=blue, group=l];
	threec [shape=circle, label="3c", fontcolor=blue, group=r];
	}
	{rank=same;
	threef [shape=circle, label="3f", fontcolor=blue, group=l];
	fivef [shape=circle, label="5f", fontcolor=blue, group=r];
	threee [shape=circle, label="3e", fontcolor=blue, group=3];
	foure [shape=circle, label="4e", fontcolor=blue, group=4];
	}
	{rank=same;
	fiveh [shape=circle, label="5h", fontcolor=blue, group=l];
	6 [shape=circle, label="6", fontcolor=blue, group=r];
	fiveg [shape=circle, label="5g", fontcolor=blue, group=3];
	fourg [shape=circle, label="4g", fontcolor=blue, group=4];
	}
	
	1->2[label="a", fontcolor=blue];
	1->threeb[label="b", fontcolor=blue];
	2->threec[label="c", fontcolor=blue, dir=back];
	2->fourd[label="d", fontcolor=blue, dir=back];
	threee->foure[label="e", fontcolor=blue, dir=back];
	threef->fivef[label="f", fontcolor=blue];
	fourg->fiveg[label="g", fontcolor=blue];
	fiveh->6[label="h", fontcolor=blue, dir=back];
	threeb->threef[style=invis];
	threef->fiveh[style=invis];
}