1 1
a
b
c
0 1 0 0 1 1 0 1
l
x a a
0 1 0 0 0 a x x
a a
l l
l
x b b
0 1 0 x 1 b 0 0
b b
l l
l
x c c
0 1 0 c x c c x
c c
l l
l
0 0 0 0 1 0 1 0
c c
c
b b
b
a a
a