Question: You have some pieces (blocked cells) on a chessboard and a castle. Show at least in have many moves the castle can move to the given destination.

Input specification: You will be first given 4 integers (x,y) coordinates of starting and destination cells. Then you will be given an integer (n) the number of blocked cells. Each of the following n lines will provide two integers (x,y) coordinates of the blocked cells.

Output specification: Show one integer, the length of shortest path. Show -1, if there is no path.