mem(0,[0]). mem(1,[1]). mem(2,[2]). mem(3,[3]). mem(4,[4]). mem(0,[0,0]). mem(0,[0,1]). mem(0,[0,2]). mem(1,[0,1]). mem(0,[1,0]). mem(0,[2,0]). mem(1,[1,1]). mem(1,[2,1]). mem(1,[1,2]). mem(2,[2,2]). mem(2,[3,2]). mem(2,[2,3]). mem(3,[2,3]). mem(3,[4,2,3]).