make-paths-3
Source: hackerearth
Difficulty: HARD

Walter White and Jesse Pinkman have now established their bases at different places.  
Now they want to form a network, that is, they want that all their bases should be reachable from every base. 
One base is reachable from other base if there is a path of tunnels connecting bases.  
Bases are suppose based on a 2-D plane having integer coordinates.   
Cost of building tunnels between two bases are coordinates (x1,y1) and (x2,y2) is min{ |x1-x2|, |y1-y2| }.  

What is the minimum cost such that a network is formed.   

Input: 
First line contains N, the number of bases.  
Each of the next N lines contain two integers xi and yi.

Output: 
Print the minimum cost of building the network.

Constraints: 
1 ≤ N ≤ 100000  
-10^9 ≤ xi,yi ≤ 10^9

SAMPLE INPUT
2
1 5
7 8

SAMPLE OUTPUT
3