Hello, This is a problem from dhaka regional'15

problem link: Honey King

In short, in a different kind of 2D plane you are given some points(10^5 maximum) in the plane. find the minimum hexagon such that all points lie inside the hexagon.

So for a cell (x, y), there are six surrounding cells, up(x, y − 1), down(x, y + 1), up_left(x − 1, y), down_right(x + 1, y), up_right(x + 1, y − 1) and down_left(x − 1, y + 1). For points (0, 0), (−1, 0) and (−2, 2), This is the hexagon witch includes minimum number of inner hexagons. Output the minimum number of inner hexagons. so 7 is the answer in this case.

Please give me some hints.