distance :: Pos -> Pos -> Int
distance (p1, p2) (q1, q2) = abs (p1 - q1) + abs (p2 - q2)
distance :: Pos -> Pos -> Int
distance (p1, p2) (q1, q2) = abs (p1 - q1) + abs (p2 - q2)
distance (p1, p2) (q1, q2) = abs (p1 - q1) + abs (p2 - q2)