CHECKER 3 3
[0,0,1,0,-1,0] [1,0,2,0,0,1] [2,0,1,1,3,1]
[0,1,1,1,-1,1] [1,1,2,1,0,2] [2,1,1,2,3,2]
[0,2,1,2,-1,2] [1,2,2,2,0,3] [2,2,1,3,3,3]