[[[g1, x], (a, 1)], [[g1, x], (b, 2)]]
[[[g1, z], (c, 3)], [[g1, z], (l, 7)], [[g1, z], (k, 8)]]
[[[g2, x], (a, 4)]]
[[[g2, y], (a, 5)]]
[[[g2, z], (b, 6)]]

[[[g1, z], (c, **3**)] and [[g1, z], (l, **7**)]

[[[g1, x], (a, 1)], [[g1, x], (b, 2)]]

[[[g1, z], (c, 3)],[[[g2, x], (a, 4)]], [[[g2, y], (a, 5)]],[[[g2, z], (b, 6)]], [[g1, z],(l, 7)], [[g1, z], (k, 8)]]

[[[sg1, x], (a, 4)]]
[[[sg2, y], (a, 5)]]
[[[sg3, z], (b, 6)]]