r4-r1-r3,r1-r3,r2-r3
-1 -1 -1 1 -2
1 2 -1 2 -1
4 5 2 1 5
0 1 -2 3 -3
r2+r1,r4+4r1
-1 -1 -1 1 -2
0 1 -2 3 -3
0 1 -2 5 -3
0 1 -2 3 -3
r3-r2,r4-r2
-1 -1 -1 1 -2
0 1 -2 3 -3
0 0 0 2 0
0 0 0 0 0