CHECKER 4 4
[0,0,1,0,-1,0] [1,0,0,1,2,1] [2,0,3,0,1,0] [3,0,2,1,4,1]
[0,1,1,1,-1,1] [1,1,0,2,2,2] [2,1,3,1,1,1] [3,1,2,2,4,2]
[0,2,0,4,1,3] [2,2,1,3,2,4]
[1,3,0,4,2,4]