(D I) (C H) | (A B) (F G)
(D H) (C I) | (A F) (B G)
-------------------------
(A H) (F I) | (C D) (E G)
(F H) (A I) | (D E) (C G)
-------------------------
(B I) (E H) | (C F) (A D)
(B E) (H I) | (A C) (D F)
-------------------------
(B D) (G H)
(D G) (B H)
-----------
(E F) (B C)
(C E) (B F)
-----------
(E I) (A G)
(G I) (A E)