x 0 2/3 a
0 x 1/3 a
-x -x 0 a
x 0 1/6 b
0 x 5/6 b
-x -x 1/2 b
x y z c
-y x-y z+2/3 c
-x+y -x z+1/3 c
y x -z c
x-y -y -z+1/3 c
-x -x+y -z+2/3 c