//x = 1 // y = 0 x1->1x x0->0x y1->1y y0->0y 0y->*0 1y->*1 0x->*1 1x->*1 0@->@0 1@->@1 |*->@ 1|->|x 0|->|y |0->| *1->1 *0->0 @0->@ @1->.1 |1->.1 @->.0
