v 1.0 1.0 1.0 v -1.0 -1.0 1.0 v -1.0 1.0 -1.0 v 1.0 -1.0 -1.0 l 1 2 l 1 3 l 1 4 l 2 1 l 2 3 l 2 4 l 3 1 l 3 2 l 3 4 l 4 1 l 4 2 l 4 3