import java.io.InputStream;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		int N = sc.nextInt();
		
		List<int[]> a = new ArrayList<>();
		for(int i=0;i<N;i++) {
			a.add(new int[] {i, sc.nextInt(), sc.nextInt()});
		}
		
		List<int[]> edges = new ArrayList<>();

		a.sort((x,y)->Integer.compare(x[1], y[1]));
		for(int i=0;i<N-1;i++) {
			edges.add(new int[] {a.get(i)[0], a.get(i+1)[0], Math.abs(a.get(i)[1] - a.get(i+1)[1])});
		}
		
		a.sort((x,y)->Integer.compare(x[2], y[2]));
		for(int i=0;i<N-1;i++) {
			edges.add(new int[] {a.get(i)[0], a.get(i+1)[0], Math.abs(a.get(i)[2] - a.get(i+1)[2])});
		}
		
		edges.sort((x,y)->Integer.compare(x[2], y[2]));

		long ans = 0;
		
		UnionFind uf = new UnionFind(N+1);
		for(int[] e : edges) {
			int x = e[0];
			int y = e[1];
			int w = e[2];
			
			if(!uf.same(x, y)) {
				uf.unite(x, y);
				ans += w;
			}
		}
		
		out.println(ans);
		
		sc.close();

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}

	@SuppressWarnings("unused")
	private String join(String delimiter, int[] a) {
		StringBuilder sb = new StringBuilder();

		for (int i = 0; i < a.length; i++) {
			sb.append(a[i]);
			sb.append(delimiter);
		}
		return sb.substring(0, Math.max(sb.length() - delimiter.length(), 0));
	}

	@SuppressWarnings("unused")
	private String join(String delimiter, long[] a) {
		StringBuilder sb = new StringBuilder();

		for (int i = 0; i < a.length; i++) {
			sb.append(a[i]);
			sb.append(delimiter);
		}
		return sb.substring(0, Math.max(sb.length() - delimiter.length(), 0));
	}

	@SuppressWarnings("unused")
	private int max(int[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		int candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate > arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private long max(long[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		long candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate > arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private int min(int[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		int candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate < arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private long min(long[] arr) {
		if(arr == null || arr.length == 0) {
			throw new IllegalArgumentException(Arrays.toString(arr));
		}

		long candidate = arr[0];
		for(int i=1;i<arr.length;i++) {
			candidate = candidate < arr[i] ? candidate : arr[i];
		}
		return candidate;
	}

	@SuppressWarnings("unused")
	private int[] nextIntArray(Scanner sc, int n) {
		int[] result = new int[n];
		for (int i = 0; i < n; i++) {
			result[i] = sc.nextInt();
		}
		return result;
	}

	@SuppressWarnings("unused")
	private long[] nextLongArray(Scanner sc, int n) {
		long[] result = new long[n];
		for (int i = 0; i < n; i++) {
			result[i] = sc.nextLong();
		}
		return result;
	}

	@SuppressWarnings("unused")
	private int[] nextIntArray1origin(Scanner sc, int n) {
		int[] result = new int[n + 1];
		for (int i = 1; i <= n; i++) {
			result[i] = sc.nextInt();
		}
		return result;
	}
}
class UnionFind {

	int[] par;

	public UnionFind(int size) {
		par = new int[size];
		Arrays.fill(par, -1);
	}

	public int root(int x) {
		if(par[x]<0) {
			return x;
		}
		int z = root(par[x]);
		par[x] = z;
		return z;
	}

	public boolean same(int a, int b) {
		return root(a) == root(b);
	}

	public void unite(int a, int b) {
		if(!same(a,b)) {
			int ra = root(a);
			int rb = root(b);

			if(par[ra] < par[rb]) {
				par[ra] += par[rb];
				par[rb] = ra;
			}else {
				par[rb] += par[ra];
				par[ra] = rb;
			}
		}
	}

	public int size(int a) {
		return -par[root(a)];
	}



}


Measured memory_bytes: 96300