979. Galaxy

You are observing a distant galaxy using a telescope above the Astronomy Tower, and you think that a rectangle drawn in that galaxy whose edges are parallel to coordinate axes and contain maximum star systems on its edges has a great deal to do with the mysteries of universe. However you do not have the laptop with you, thus you have written the coordinates of all star systems down on a piece of paper and decide to work out the result later. Can you finish this task?

Input file starts with one integer `N` (`1\ ≤\ N\ ≤\ 250`), the number of star systems on the telescope. `N` lines follow, each line consists of two integers: the `X` and `Y` coordinates of the `K`th planet system. The absolute value of any coordinate is no more than `10^9`, and you can assume that the planets are arbitrarily distributed in the universe.

Output the maximum value you have found.

10
2 3
9 2
7 4
3 4
5 7
1 5
10 4
10 6
11 4
4 6

7