DCEL 0 S edge_0 0->edge_0 edge_7 0->edge_7 1 E edge_3 1->edge_3 2 P1 edge_2 2->edge_2 edge_5 2->edge_5 3 P2 edge_4 3->edge_4 edge_1 3->edge_1 4 B edge_6 4->edge_6 edge_0->3 0 edge_0->edge_4 edge_4->2 4 edge_4->edge_3 edge_1->0 1 edge_1->edge_0 edge_2->1 2 edge_2->edge_1 edge_3->2 3 edge_3->edge_5 edge_5->3 5 edge_5->edge_1 edge_6->0 6 edge_6->edge_7 edge_7->4 7 edge_7->edge_6