using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
using static Template;

namespace SolveSpace
{
    using static System.Console;
    using static System.Convert;
    using static System.Math;
    using Pi = Pair<int, int>;
    using Number = System.Int64;

    class Solver
    {
        public void Solve()
        {
            var num = Input.num;
            var xy = new Pair<int, int, int>[num];
            for (var i = 0; i < num; i++)
                xy[i] = new Pair<int, int, int>(Input.Next<int>(), Input.Next<int>(), i);
            var k = new Kruskal(num);
            var uf = new UnionFind(num);
            Array.Sort(xy, (a, b) => a.v1 - b.v1);
            for (var i = 0; i < num - 1; i++)
                k.AddEdge(xy[i].v3, xy[i + 1].v3, xy[i + 1].v1 - xy[i].v1);
            Array.Sort(xy, (a, b) => a.v2 - b.v2);
            for (var i = 0; i < num - 1; i++)
                k.AddEdge(xy[i].v3, xy[i + 1].v3, xy[i + 1].v2 - xy[i].v2);
            WriteLine(k.Execute());
        }
    }
    /// <summary>
    /// 依存:UnionFind
    /// </summary>
    class Kruskal
    {
        private int num;
        private List<Pair<int, int, Number>> edges;
        public Kruskal(int num)
        { this.num = num;edges = new List<Pair<int, int, Number>>(); }
        public void AddEdge(int u, int v, Number weight)
            => edges.Add(new Pair<int, int, Number>(u, v, weight));
        public Number Execute()
        {
            edges.Sort((a, b) => a.v3.CompareTo(b.v3));
            Number res = 0;
            var uf = new UnionFind(num);
            foreach (var e in edges)
                if (uf.Union(e.v1, e.v2))
                    res += e.v3;
            return res;
        }
    }
}

public class UnionFind
{
    protected int[] parent, size, rank;
    public UnionFind(int num)
    {
        parent = new int[num]; size = new int[num]; rank = new int[num];
        for (var i = 0; i < num; i++) { parent[i] = i; size[i] = 1; }
    }
    protected int Find(int i)
        => i == parent[i] ? i : (parent[i] = Find(parent[i]));
    public int Parent(int i)
        => Find(i);
    public int Size(int i)
        => size[Find(i)];
    public virtual bool Union(int v1, int v2)
    {
        v1 = Find(v1); v2 = Find(v2);
        if (v1 == v2) return false;
        if (rank[v1] < rank[v2])
            swap(ref v1, ref v2);
        parent[v2] = v1;
        size[v1] += size[v2];
        if (rank[v1] == rank[v2])
            rank[v1]++;
        return true;
    }
    public bool IsSame(int v1, int v2)
        => Find(v1) == Find(v2);
}

#region Template
public class Template
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmin<T>(ref T num, T val) where T : IComparable<T>
    { if (num.CompareTo(val) == 1) { num = val; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmax<T>(ref T num, T val) where T : IComparable<T>
    { if (num.CompareTo(val) == -1) { num = val; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void swap<T>(ref T v1, ref T v2)
    { var t = v2; v2 = v1; v1 = t; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static T[] Create<T>(int n, Func<T> f)
        => Enumerable.Repeat(0, n).Select(_ => f()).ToArray();
    public static void Fail() => Fail("No");
    public static void Fail<T>(T s) { Console.WriteLine(s); Console.Out.Close(); Environment.Exit(0); }
    static void Main(string[] args)
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);
        var p = new SolveSpace.Solver();
        for (var i = 1; i > 0; --i)
            p.Solve();
        Console.Out.Flush();
    }
}

public class Input
{
    public static string read => Console.ReadLine().Trim();
    public static int[] ar => read.Split(' ').Select(int.Parse).ToArray();
    public static int num => Convert.ToInt32(read);
    public static long[] arL => read.Split(' ').Select(long.Parse).ToArray();
    public static long numL => Convert.ToInt64(read);
    public static char[][] grid(int h)
        => Create(h, () => read.ToCharArray());
    public static int[] ar1D(int n)
        => Create(n, () => num);
    public static long[] arL1D(int n)
        => Create(n, () => numL);
    public static string[] strs(int n)
        => Create(n, () => read);
    public static int[][] ar2D(int n)
        => Create(n, () => ar);
    public static long[][] arL2D(int n)
        => Create(n, () => arL);
    public static List<T>[] edge<T>(int n)
        => Create(n, () => new List<T>());
    public static void Make<T1, T2>(out T1 v1, out T2 v2)
    {
        v1 = Next<T1>();
        v2 = Next<T2>();
    }
    public static void Make<T1, T2, T3>(out T1 v1, out T2 v2, out T3 v3)
    {
        Make(out v1, out v2);
        v3 = Next<T3>();
    }
    public static void Make<T1, T2, T3, T4>(out T1 v1, out T2 v2, out T3 v3, out T4 v4)
    {
        Make(out v1, out v2, out v3);
        v4 = Next<T4>();
    }
    public static void Make<T1, T2, T3, T4, T5>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5)
    {
        Make(out v1, out v2, out v3, out v4);
        v5 = Next<T5>();
    }
    public static void Make<T1, T2, T3, T4, T5, T6>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5, out T6 v6)
    {
        Make(out v1, out v2, out v3, out v4, out v5);
        v6 = Next<T6>();
    }
    static Input()
    {
        sc = new Queue<string>();
        dic = new Dictionary<Type, Func<string, object>>();
        dic[typeof(int)] = s => int.Parse(s);
        dic[typeof(long)] = s => long.Parse(s);
        dic[typeof(char)] = s => char.Parse(s);
        dic[typeof(double)] = s => double.Parse(s);
        dic[typeof(uint)] = s => uint.Parse(s);
        dic[typeof(ulong)] = s => ulong.Parse(s);
        dic[typeof(string)] = s => s;
    }
    private static Dictionary<Type, Func<string, object>> dic;
    private static Queue<string> sc;
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static T Next<T>() { if (sc.Count == 0) foreach (var item in read.Split(' ')) sc.Enqueue(item); return (T)dic[typeof(T)](sc.Dequeue()); }
    public const int MOD = 1000000007;
}

public class Pair<T1, T2> : IComparable<Pair<T1, T2>>
{
    public T1 v1;
    public T2 v2;
    public Pair() { v1 = Input.Next<T1>(); v2 = Input.Next<T2>(); }
    public Pair(T1 v1, T2 v2)
    { this.v1 = v1; this.v2 = v2; }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public int CompareTo(Pair<T1, T2> p)
    {
        var c = Comparer<T1>.Default.Compare(v1, p.v1);
        if (c == 0)
            c = Comparer<T2>.Default.Compare(v2, p.v2);
        return c;
    }
    public override string ToString()
        => $"{v1.ToString()} {v2.ToString()}";
}

public class Pair<T1, T2, T3> : Pair<T1, T2>, IComparable<Pair<T1, T2, T3>>
{
    public T3 v3;
    public Pair() : base() { v3 = Input.Next<T3>(); }
    public Pair(T1 v1, T2 v2, T3 v3) : base(v1, v2)
    { this.v3 = v3; }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public int CompareTo(Pair<T1, T2, T3> p)
    {
        var c = base.CompareTo(p);
        if (c == 0)
            c = Comparer<T3>.Default.Compare(v3, p.v3);
        return c;
    }
    public override string ToString()
        => $"{base.ToString()} {v3.ToString()}";
}
#endregion


Measured memory_bytes: 35256