c-c-c-c- x-x-x-x- z-z-z-z- c---- [ic]-c-c-c i [ux]-x-x-x u [yz]-z-z-z y [ic]---- [ic] - v b v b i u----u [yc] v b B v - y i---- [ic]-c v b v b i [ux]-x-x-x u [yc] v b B v-z y [ic]---- [ic] - v b v b i u----u [yc] v b B v - y i---- [ic] c c v b v b [ic] [ux] x x x x x x [ux] [yc] v b B v z z [yz] [ic]---- c-c-c-c- x-x-x-x- z-z-z-z- c