3

# r1
4 4
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1

# r2
4 4
1 1 0 0
1 0 0 0
0 0 1 0
0 0 0 1

# D
4 5
1  1  0  0 0  # i >= 0
1 -1  0  1 0 # i <= N
1  0  1  0 0 # j >= 0
1  0 -1  1 0 # j <= N

#context
1 3
1 1 -3 # n>=3
