Usage

java -jar gauss.jar "[[0, 0, 0, 0, 3, 3, 1, 1],[3, 0, 1, 0, 0, 0, 0, 0],[0, 3, 0, 1, 3, 0, 1, 0],[0, 1, 0, 4, 3, 1, 2, 0],[0, 3, 3, 3, 1, 1, 1, 0],[0, 3, 0, 1, 0, 0, 0, 0]]" 5

Output

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

Or more readable version

IN

0 0 0 0 3 3 1 1
3 0 1 0 0 0 0 0
0 3 0 1 3 0 1 0
0 1 0 4 3 1 2 0
0 3 3 3 1 1 1 0
0 3 0 1 0 0 0 0

OUT

3 0 0 0 0 0 4 0
0 3 0 0 0 0 2 1
0 0 3 0 0 0 3 0
0 0 0 2 0 0 1 3
0 0 0 0 3 0 1 0
0 0 0 0 0 3 0 1