“…Let D and D ′ be two lists of integers. The inclusion D ′ ⊆ D means that D ′ is a sublist of D. In this case D − D ′ is the complementary sublist of D ′ in D. For instance, the sublists of D = [1,1,2] are the empty list [ ], [1] (twice), [2], [1,1], [1,2] (twice) and D itself. Their complementary sublists in the same order are D, [1,2] (twice), [1,1], [2], [1] (twice) and [ ].…”