C, E, F, G, H, c, e, f, g, h, 
-C*e+E*c+C-E
F-C
E-G
-E*f+E*h+F*e-F*h-H*e+H*f
-F*g+G*f
-G*h+H*g+G-H
-C*h+H*c
