题目描述
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
输入格式
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输出格式
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