using System;
using System.Linq;
using System.Collections.Generic;
namespace Contest
{
class Program
{
static void Main(string[] args)
{
ARC076.D();
}
class ARC076
{
public static void C()
{
var N = Read.Int();
var M = Read.Int();
if (Math.Abs(N - M) > 1) { Console.WriteLine(0);return; }
long ans = 1;
long P = 1000000007;
for (int i = 1; i <= N; ++i)
{
ans = (ans * i) % P;
}
for (int i = 1; i <= M; ++i)
{
ans = (ans * i) % P;
}
if (N == M) { ans = (ans * 2) % P; }
Console.WriteLine(ans);
}
public static void D()
{
var N = Read.Int();
var XY = Read.TupleLong(N);
Tuple<long, int>[] X = Enumerable.Range(0, N).Select(i => new Tuple<long, int>(XY[i].Item1, i)).ToArray();
Tuple<long, int>[] Y = Enumerable.Range(0, N).Select(i => new Tuple<long, int>(XY[i].Item2, i)).ToArray();
Array.Sort(X, (a, b) => a.Item1.CompareTo(b.Item1));
Array.Sort(Y, (a, b) => a.Item1.CompareTo(b.Item1));
List<Tuple<long, int, int>> edge = new List<Tuple<long, int, int>>();
for(int i = 0; i < N - 1; ++i)
{
edge.Add(new Tuple<long, int, int>(X[i + 1].Item1 - X[i].Item1, X[i].Item2, X[i + 1].Item2));
edge.Add(new Tuple<long, int, int>(Y[i + 1].Item1 - Y[i].Item1, Y[i].Item2, Y[i + 1].Item2));
}
var sortedEdge = edge.ToArray();
Array.Sort(sortedEdge, (a, b) => a.Item1.CompareTo(b.Item1));
var uft = new Util.UnionFindTree(N);
long sum = 0;
foreach(var e in sortedEdge)
{
if (uft.Root(e.Item2) != uft.Root(e.Item3))
{
uft.Unite(e.Item2, e.Item3);
sum += e.Item1;
}
}
Console.WriteLine(sum);
}
}
class Util
{
public class UnionFindTree
{ //各Treeのサイズを保持する拡張仕様
int[] parent;
int[] count;
public UnionFindTree(int n) { parent = new int[n]; count = new int[n]; for (int i = 0; i < n; ++i) { parent[i] = i; count[i] = 1; } }
public int Root(int i) { if (parent[i] == i) { return i; } else { return parent[i] = Root(parent[i]); } }
public int Count(int i) { return count[Root(i)]; }
public bool Same(int i, int j) { return Root(i) == Root(j); }
public void Unite(int i, int j) { var ri = Root(i); var rj = Root(j); if (ri != rj) { parent[ri] = rj; count[rj] += count[ri]; } }
}
}
static class Read
{
static Queue<string> queue = new Queue<string>();
static void Enqueue() { var ss = Console.ReadLine().Split(' '); foreach (var s in ss) { queue.Enqueue(s); } }
public static int Int() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt32(queue.Dequeue()); }
public static long Long() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt64(queue.Dequeue()); }
public static string Str() { if (queue.Count == 0) { Enqueue(); } return queue.Dequeue(); }
public static int[] IntN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray(); }
public static long[] LongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray(); }
public static string[] StrN() { return Console.ReadLine().Split(' '); }
public static Tuple<int, int>[] TupleInt(int n) { List<Tuple<int, int>> list = new List<Tuple<int, int>>(); for (int i = 0; i < n; ++i) { var ab = Read.IntN(); list.Add(new Tuple<int, int>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<long, long>[] TupleLong(int n) { List<Tuple<long, long>> list = new List<Tuple<long, long>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<long, long>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<string, string>[] TupleStr(int n) { List<Tuple<string, string>> list = new List<Tuple<string, string>>(); for (int i = 0; i < n; ++i) { var ab = Read.StrN(); list.Add(new Tuple<string, string>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<double, double>[] TupleDouble(int n) { List<Tuple<double, double>> list = new List<Tuple<double, double>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<double, double>(ab[0], ab[1])); } return list.ToArray(); }
public static long[,] LongMatrix(int r, int c)
{
var mat = new long[r, c];
for (int i = 0; i < r; ++i)
{
var x = Read.LongN();
for (int j = 0; j < c; ++j)
{
mat[i, j] = x[j];
}
}
return mat;
}
public static Dictionary<int, HashSet<int>> AdjacencyList(int N, int M)
{
Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
for (int i = 0; i <= N; ++i)
{
dict.Add(i, new HashSet<int>());
}
for (int i = 0; i < M; ++i)
{
var ab = Read.IntN();
dict[ab[0]].Add(ab[1]);
dict[ab[1]].Add(ab[0]);
}
return dict;
}
public static Dictionary<int, Dictionary<int, long>> AdjacencyListWithWeight(int N, int M)
{
Dictionary<int, Dictionary<int, long>> dict = new Dictionary<int, Dictionary<int, long>>();
for (int i = 0; i <= N; ++i)
{
dict.Add(i, new Dictionary<int, long>());
}
for (int i = 0; i < M; ++i)
{
var ab = Read.IntN();
dict[ab[0]].Add(ab[1], ab[2]);
dict[ab[1]].Add(ab[0], ab[2]);
}
return dict;
}
}
}
}