coz after 4 iteration will ends the matrix .if you count 6*6 matrix and if you need only 3*3 than it will be possible only uptu 4 iterartion

9 -9 -9 1 1 1 0 -9 0 4 3 2 -9 -9 -9 1 2 3 0 0 8 6 6 0 -->>4th line 0 0 0 -2 0 0 0 0 1 2 4 0

you can iterate til 4th line because next iteration give 2 lines only