fact: Definition to4i l c l1 n:= match c, l with | TO4 m _ _, O1 :: l2 => to3i l2 m l1 n | TO4 _ m _, O2 :: l2 => to3i l2 m l1 n | TO4 _ _ m, O3 :: l2 => to3i l2 m l1 n | _, _ => false end.
imports: PrimInt63 Cyclic63 List BasicRubik