Bad_Cells

You are given an infinite checkered field. You should get from a square ( x 1; y 1) to a square ( x 2; y 2). Using the shortest path is not necessary. You can move on to the field squares in four directions. That is, when you are positioned in any square, you can move to any other side-neighboring one. A square ( x; y) is considered bad if at least one of the two conditions is fulfilled: |x