20
0 -1 -4 -1
1 -1 5 -1
0 2 -4 2
1 2 5 2
-1 0 -1 -4
-1 1 -1 5
2 0 2 -4
2 1 2 5
-2 2 2 -2
-1 3 3 -1
-2 -1 2 3
3 2 -1 -2
0 -1 0 3
-1 1 3 1
1 -2 1 2
-2 0 2 0
-1 4 3 0
3 1 -1 -3
2 -3 -2 1
-3 -1 1 3