5_1, 6_1			5_4, 6_4	5_5, 6_5	5_6, 6_6	5_7, 6_7
1_1	1_2, 1_3		1_4, 2_4, 3_4	1_5	1_6, 2_6
2_1	2_2				1_6, 2_6
3_1	3_2	3_3		3_5, 4_5	3_6
4_1	4_2	4_3, 4_4		3_5, 4_5	4_6	4_7
5_1, 6_1	5_2, 5_3, 6_2, 6_3		5_4, 6_4	5_5, 6_5	5_6, 6_6	5_7, 6_7