// ReSharper disable ArrangeTypeMemberModifiers
// ReSharper disable ConvertIfStatementToSwitchStatement
// ReSharper disable FunctionRecursiveOnAllPaths
// ReSharper disable InconsistentNaming
// ReSharper disable InlineOutVariableDeclaration
// ReSharper disable InvertIf
// ReSharper disable JoinDeclarationAndInitializer
// ReSharper disable MemberCanBeMadeStatic.Global
// ReSharper disable MemberCanBeMadeStatic.Local
// ReSharper disable NonReadonlyMemberInGetHashCode
// ReSharper disable PossibleNullReferenceException
// ReSharper disable RedundantUsingDirective
// ReSharper disable SuggestVarOrType_BuiltInTypes
// ReSharper disable SuggestVarOrType_Elsewhere
// ReSharper disable TailRecursiveCall
// ReSharper disable UnusedMember.Global
// ReSharper disable UnusedMember.Local
// ReSharper disable UseObjectOrCollectionInitializert

#if true && UTAKA_LOCAL

//#if false
#define UTAKA_DEBUG
#endif

//#define TOPCODER

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Numerics;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using static UtakaApp.Util;

namespace UtakaApp
{
    public partial class Program
    {
        /*
        https://atcoder.jp/contests/abc065/tasks/arc076_b
        */

        public const string SiteName    = "AtCoder";
        public const string ContestName = "arc076";
        public const string ProblemName = "D";

        public int N;

        public Point[] points;

        public void Solve()
        {
            N      = cin.ReadInt;
            points = new Point[N];

            for (int i = 0; i < N; i++)
            {
                points[i] = new Point(i, cin.ReadInt, cin.ReadInt);
            }

            Point[] xSorted = new Point[N];
            Point[] ySorted = new Point[N];

            xSorted = points.Copy();
            ySorted = points.Copy();

            Array.Sort(xSorted, (a, b) =>
            {
                if (a.X < b.X) return -1;
                if (a.X > b.X) return 1;

                return a.Id - b.Id;
            });

            Array.Sort(ySorted, (a, b) =>
            {
                if (a.Y < b.Y) return -1;
                if (a.Y > b.Y) return 1;

                return a.Id - b.Id;
            });

            List<Edge>[] edges = new List<Edge>[N];

            for (int i = 0; i < N; i++)
            {
                edges[i] = new List<Edge>();
            }

            for (int i = 0; i < N - 1; i++)
            {
                Point px1 = xSorted[i];
                Point px2 = xSorted[i + 1];
                Point py1 = ySorted[i];
                Point py2 = ySorted[i + 1];

                edges[px1.Id].Add(new Edge(Math.Abs(px1.X - px2.X), px1.Id, px2.Id));
                edges[px2.Id].Add(new Edge(Math.Abs(px1.X - px2.X), px2.Id, px1.Id));
                edges[py1.Id].Add(new Edge(Math.Abs(py1.Y - py2.Y), py1.Id, py2.Id));
                edges[py2.Id].Add(new Edge(Math.Abs(py1.Y - py2.Y), py2.Id, py1.Id));
            }
            long ans = new Prim().CalcTotalCost(edges, 0);

            cou.WriteLine(ans);
        }
    }

    public class Prim
    {
        public long CalcTotalCost(List<Edge>[] edges, int initialIndex)
        {
            int n = edges.Length;

            var pq = new PriorityQueue<Edge>();

            // はじめはinitialIndexからinitialIndexまで、コスト0のedgeを入れておく
            pq.Enqueue(new Edge(0, initialIndex, initialIndex));

            long totalCost = 0;

            bool[] used = new bool[n];

            while (pq.Count > 0)
            {
                var edge = pq.Dequeue();

                if (used[edge.T]) continue;

                used[edge.T] = true;

                totalCost += edge.Cost;

                foreach (Edge e in edges[edge.T])
                {
                    pq.Enqueue(e);
                }
            }

            return totalCost;
        }
    }

    public class PriorityQueue<T> where T : IComparable<T>
    {
        private List<T> data;

        public PriorityQueue()
        {
            this.data = new List<T>();
        }

        public void Enqueue(T item)
        {
            data.Add(item);
            int ci = data.Count - 1; // child index; start at end
            while (ci > 0)
            {
                int pi = (ci - 1) / 2; // parent index
                if (data[ci].CompareTo(data[pi]) >= 0)
                    break; // child item is larger than (or equal) parent so we're done
                T tmp = data[ci];
                data[ci] = data[pi];
                data[pi] = tmp;
                ci       = pi;
            }
        }

        public T Dequeue()
        {
            // assumes pq is not empty; up to calling code
            int li        = data.Count - 1; // last index (before removal)
            T   frontItem = data[0];        // fetch the front
            data[0] = data[li];
            data.RemoveAt(li);

            --li;       // last index (after removal)
            int pi = 0; // parent index. start at front of pq
            while (true)
            {
                int ci = pi * 2 + 1; // left child index of parent
                if (ci > li)
                    break;       // no children so done
                int rc = ci + 1; // right child
                if (rc <= li && data[rc].CompareTo(data[ci]) < 0
                ) // if there is a rc (ci + 1), and it is smaller than left child, use the rc instead
                    ci = rc;
                if (data[pi].CompareTo(data[ci]) <= 0)
                    break; // parent is smaller than (or equal to) smallest child so done
                T tmp = data[pi];
                data[pi] = data[ci];
                data[ci] = tmp; // swap parent and child
                pi       = ci;
            }

            return frontItem;
        }

        public T Peek()
        {
            T frontItem = data[0];
            return frontItem;
        }

        public int Count => data.Count;

        public override string ToString()
        {
            string s = "";
            for (int i = 0; i < data.Count; ++i)
                s += data[i].ToString() + " ";
            s += "count = " + data.Count;
            return s;
        }
    }


    public struct Edge : IComparable<Edge>, IEquatable<Edge>
    {
        public long Cost;
        public int  F;
        public int  T;

        public Edge(long cost, int f, int t)
        {
            Cost = cost;
            F    = f;
            T    = t;
        }

        public int CompareTo(Edge other)
        {
            if (Cost < other.Cost) return -1;
            if (Cost > other.Cost) return 1;

            int secondComparison = F - other.F;
            if (secondComparison != 0)
            {
                return secondComparison;
            }

            int thirdComparison = T - other.T;
            return thirdComparison;
        }

        public bool Equals(Edge other)
        {
            return Cost == other.Cost && F == other.F && T == other.T;
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj))
            {
                return false;
            }

            return obj is Edge && Equals((Edge)obj);
        }

        public override int GetHashCode()
        {
            unchecked
            {
                var hashCode = Cost.GetHashCode();
                hashCode = (hashCode * 397) ^ F;
                hashCode = (hashCode * 397) ^ T;
                return hashCode;
            }
        }

        public override string ToString()
        {
            return $"{nameof(Cost)}: {Cost}, {nameof(F)}: {F}, {nameof(T)}: {T}";
        }
    }


    public sealed class Point : Pair<long, long>
    {
        public int Id;

        public Point(int id, long x, long y) : base(x, y)
        {
            Id = id;
        }

        private bool Equals(Point other)
        {
            return Id == other.Id;
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj))
            {
                return false;
            }

            if (ReferenceEquals(this, obj))
            {
                return true;
            }

            return obj is Point && Equals((Point)obj);
        }

        public override int GetHashCode()
        {
            return Id;
        }
    }

    [DebuggerDisplay("({X}, {Y})")]
    public abstract class Pair<T1, T2> : IComparable<Pair<T1, T2>>
        where T1 : IComparable<T1>
        where T2 : IComparable<T2>
    {
        public Pair(T1 x, T2 y)
        {
            X = x;
            Y = y;
        }

        public T1 X;
        public T2 Y;

        public int CompareTo(Pair<T1, T2> other)
        {
//            if (ReferenceEquals(this, other)) return 0;
//            if (ReferenceEquals(null, other)) return 1;
            var firstComparison = X.CompareTo(other.X);
            return firstComparison != 0 ? firstComparison : Y.CompareTo(other.Y);
        }

        public override string ToString() => $"({X}, {Y})";

//        public bool Equals(Pair<T1, T2> other)
//        {
//            if (ReferenceEquals(null, other)) return false;
//            if (ReferenceEquals(this, other)) return true;
//            return EqualityComparer<T1>.Default.Equals(X, other.X) &&
//                   EqualityComparer<T2>.Default.Equals(Y, other.Y);
//        }

//        public override bool Equals(object obj)
//        {
//            if (ReferenceEquals(null, obj)) return false;
//            if (ReferenceEquals(this, obj)) return true;
//            return obj.GetType() == this.GetType() && Equals((Pair<T1, T2>)obj);
//        }

//        public override int GetHashCode()
//        {
//            unchecked
//            {
//                return (EqualityComparer<T1>.Default.GetHashCode(X) * 397) ^
//                       EqualityComparer<T2>.Default.GetHashCode(Y);
//            }
//        }
    }


//=========================================================================================
// Debug IO
//=========================================================================================

    public partial class Program
    {
        //=========================================================================================
        // Main
        //=========================================================================================

        private readonly ConsoleInput cin;
        private readonly IConsole     cou;

        public Program(ConsoleInput cin, IConsole cou)
        {
            this.cin = cin;
            this.cou = cou;
        }

#if !TOPCODER
        public static void Main(string[] args)
        {
#if UTAKA_LOCAL
//#if false
            new TestCaseCheckerForAtCoder().TestProblems();
#else
            var cin = new ConsoleInput(System.Console.In);
            var console = new MyConsole();
            new Program(cin, console).Solve();
            console.Flush();
#endif
        }
#endif

        public void WriteEnumerable<T>(IEnumerable<T> A, string delimiter = " ")
        {
            var sb = new StringBuilder();
            foreach (T v in A)
            {
                sb.Append(v);
                sb.Append(delimiter);
            }

            if (sb.Length > 0)
            {
                sb.Length--;
            }

            cou.WriteLine(sb.ToString());
        }
    }

    public static class Util
    {
        //=========================================================================================
        // Library
        //=========================================================================================

        public static T[] Array1D<T>(int a, T defaultValue)
            where T : struct
        {
            var ret = new T[a];
            for (int i = 0; i < a; i++)
            {
                ret[i] = defaultValue;
            }

            return ret;
        }

        public static T[] Array1D<T>(int a)
            where T : struct
        {
            var ret = new T[a];
            return ret;
        }

        /// <summary>
        /// 要素数 (a, b) の、defaultValue で満たされた配列を作成します。
        /// </summary>
        /// <typeparam name="T">配列の型</typeparam>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <param name="defaultValue">デフォルト値</param>
        /// <returns>指定した条件で初期化された配列</returns>
        public static T[,] Array2D<T>(int a, int b, T defaultValue)
            where T : struct
        {
            var ret = new T[a, b];
            for (int i = 0; i < a; i++)
            {
                for (int j = 0; j < b; j++)
                {
                    ret[i, j] = defaultValue;
                }
            }

            return ret;
        }

        public static T[,,] Array3D<T>(int a, int b, int c, T defaultValue)
            where T : struct
        {
            T[,,] ret = new T[a, b, c];

            for (int i = 0; i < a; i++)
            {
                for (int j = 0; j < b; j++)
                {
                    for (int k = 0; k < c; k++)
                    {
                        ret[i, j, k] = defaultValue;
                    }
                }
            }

            return ret;
        }

        /// <summary>
        /// 要素数 (a, b) の、defaultValue で満たされたJag配列を作成します。
        /// </summary>
        /// <typeparam name="T">配列の型</typeparam>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <param name="defaultValue">デフォルト値</param>
        /// <returns>指定した条件で初期化された配列</returns>
        public static T[][] JagArray2D<T>(int a, int b, T defaultValue)
            where T : struct
        {
            var ret = new T[a][];
            for (int i = 0; i < a; i++)
            {
                var row = new T[b];
                ret[i] = row;

                for (int j = 0; j < b; j++)
                {
                    row[j] = defaultValue;
                }
            }

            return ret;
        }

        /// <summary>
        /// 要素数 (a, b) のdefault値で満たされたJag配列を作成します。
        /// </summary>
        /// <typeparam name="T">配列の型</typeparam>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <returns>初期化された配列</returns>
        public static T[][] JagArray2D<T>(int a, int b)
            where T : struct
        {
            var ret = new T[a][];
            for (int i = 0; i < a; i++)
            {
                ret[i] = new T[b];
            }

            return ret;
        }

        public static T[][][] JagArray3D<T>(int a, int b, int c, T defaultValue)
            where T : struct
        {
            var ret = new T[a][][];
            for (int i = 0; i < a; i++)
            {
                T[][] aRow = new T[b][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[] bRow = new T[c];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        bRow[k] = defaultValue;
                    }
                }
            }

            return ret;
        }

        public static T[][][] JagArray3D<T>(int a, int b, int c)
            where T : struct
        {
            var ret = new T[a][][];
            for (int i = 0; i < a; i++)
            {
                T[][] aRow = new T[b][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[] bRow = new T[c];
                    aRow[j] = bRow;
                }
            }

            return ret;
        }

        public static T[][][][] JagArray4D<T>(int a, int b, int c, int d, T defaultValue)
            where T : struct
        {
            var ret = new T[a][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][] aRow = new T[b][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][] bRow = new T[c][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[] cRow = new T[d];
                        bRow[k] = cRow;

                        for (int l = 0; l < d; l++)
                        {
                            cRow[l] = defaultValue;
                        }
                    }
                }
            }

            return ret;
        }

        public static T[][][][] JagArray4D<T>(int a, int b, int c, int d)
            where T : struct
        {
            var ret = new T[a][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][] aRow = new T[b][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][] bRow = new T[c][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[] cRow = new T[d];
                        bRow[k] = cRow;
                    }
                }
            }

            return ret;
        }

        public static T[][][][][] JagArray5D<T>(int a, int b, int c, int d, int e, T defaultValue)
            where T : struct
        {
            var ret = new T[a][][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][][] aRow = new T[b][][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][][] bRow = new T[c][][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[][] cRow = new T[d][];
                        bRow[k] = cRow;

                        for (int l = 0; l < d; l++)
                        {
                            T[] dRow = new T[e];
                            cRow[l] = dRow;

                            for (int m = 0; m < e; m++)
                            {
                                dRow[m] = defaultValue;
                            }
                        }
                    }
                }
            }

            return ret;
        }

        public static T[][][][][] JagArray5D<T>(int a, int b, int c, int d, int e)
            where T : struct
        {
            var ret = new T[a][][][][];
            for (int i = 0; i < a; i++)
            {
                T[][][][] aRow = new T[b][][][];
                ret[i] = aRow;

                for (int j = 0; j < b; j++)
                {
                    T[][][] bRow = new T[c][][];
                    aRow[j] = bRow;

                    for (int k = 0; k < c; k++)
                    {
                        T[][] cRow = new T[d][];
                        bRow[k] = cRow;

                        for (int l = 0; l < d; l++)
                        {
                            T[] dRow = new T[e];
                            cRow[l] = dRow;
                        }
                    }
                }
            }

            return ret;
        }

        /// <summary>
        /// ジャグ配列をコピーして返す。
        /// </summary>
        public static T[][] CopyJagArray2D<T>(T[][] source)
            where T : struct
        {
            int   len  = source.Length;
            T[][] dest = new T[len][];

            for (int i = 0; i < len; i++)
            {
                T[] inner       = source[i];
                int innerLength = inner.Length;
                T[] newer       = new T[innerLength];
                Array.Copy(inner, newer, innerLength);
                dest[i] = newer;
            }

            return dest;
        }
    }

    public class IntLargeComparer : IComparer<int>
    {
        public static IntLargeComparer Instance = new IntLargeComparer();

        public int Compare(int x, int y)
        {
            return y - x;
        }
    }

    public class LongLargeComparer : IComparer<long>
    {
        public static LongLargeComparer Instance = new LongLargeComparer();

        public int Compare(long x, long y)
        {
            if (x > y) return -1;
            if (x < y) return 1;
            return 0;
        }
    }

    public static class UtakaExtentions
    {
        /// <summary>
        /// 配列をコピーします
        /// </summary>
        public static T[] Copy<T>(this IList<T> a)
        {
            T[] ret = new T[a.Count];

            for (int i = 0; i < a.Count; i++) ret[i] = a[i];

            return ret;
        }
    }

    public class ConsoleInput
    {
        private readonly char          _separator = ' ';
        private readonly TextReader    _stream;
        private readonly Queue<string> inputStream;

        public ConsoleInput(TextReader stream, char separator = ' ')
        {
            _separator  = separator;
            _stream     = stream;
            inputStream = new Queue<string>();
        }

        public string Read
        {
            get
            {
                if (inputStream.Count != 0)
                {
                    return inputStream.Dequeue();
                }

                var tmp = _stream.ReadLine().Split(_separator);
                for (var i = 0; i < tmp.Length; ++i)
                {
                    inputStream.Enqueue(tmp[i]);
                }

                return inputStream.Dequeue();
            }
        }

        public string ReadLine   => _stream.ReadLine();
        public int    ReadInt    => int.Parse(Read);
        public long   ReadLong   => long.Parse(Read);
        public double ReadDouble => double.Parse(Read);

        public string[] ReadStrArray(long N)
        {
            var ret = new string[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = Read;
            }

            return ret;
        }

        public int[] ReadIntArray(long N)
        {
            var ret = new int[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = ReadInt;
            }

            return ret;
        }

        public int[] ReadIntArrayMinus1(long N)
        {
            var ret = new int[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = ReadInt - 1;
            }

            return ret;
        }

        public long[] ReadLongArray(long N)
        {
            var ret = new long[N];
            for (long i = 0; i < N; ++i)
            {
                ret[i] = ReadLong;
            }

            return ret;
        }
    }

    public interface IConsole
    {
        void Flush();
        void Write(object obj);
        void Write(string str);
        void WriteLine(object obj);
        void WriteLine(string str);
        void WriteLine();
    }

    public class MyConsole : IConsole
    {
        public MyConsole()
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};
            Console.SetOut(sw);
        }

        public void Flush()
        {
            Console.Out.Flush();
        }

        public void Write(object obj)
        {
            Write(obj.ToString());
        }

        public void Write(string str)
        {
            Console.Write(str);
        }

        public void WriteLine(object obj)
        {
            WriteLine(obj.ToString());
        }

        public void WriteLine(string str)
        {
            Console.WriteLine(str);
        }

        public void WriteLine()
        {
            Console.WriteLine();
        }
    }

#if UTAKA_LOCAL

    public class DebugConsole : IConsole
    {
        private readonly StringBuilder mSb;

        public DebugConsole()
        {
            mSb = new StringBuilder();
        }

        public void Flush()
        {
            // 何もしない
        }

        public void Write(object obj)
        {
            Write(obj.ToString());
        }

        public void Write(string str)
        {
            mSb.Append(str);
        }

        public void WriteLine(object obj)
        {
            WriteLine(obj.ToString());
        }

        public void WriteLine(string str)
        {
            mSb.AppendLine(str);
        }

        public void WriteLine()
        {
            mSb.AppendLine();
        }

        public string GetAllOutput()
        {
            return mSb.ToString();
        }
    }

#endif

#if UTAKA_LOCAL

    public class TestCaseCheckerForAtCoder
    {
        private string GetDirectoryPath()
        {
            var problemPart = string.IsNullOrEmpty(Program.ProblemName)
                ? ""
                : $"/{Program.ProblemName}";

            return
                $"{Environment.GetFolderPath(Environment.SpecialFolder.UserProfile)}/AlgorithmPrac/{Program.SiteName}/{Program.ContestName}{problemPart}";
        }

        private string GetInputFilePath(int testCaseNumber)
        {
            return $"{GetDirectoryPath()}/sample-{testCaseNumber}.in";
        }

        private string GetOutputFilePath(int testCaseNumber)
        {
            return $"{GetDirectoryPath()}/sample-{testCaseNumber}.out";
        }

        public bool TestProblem(int testCaseNumber)
        {
            var inputFilePath  = GetInputFilePath(testCaseNumber);
            var outputFilePath = GetOutputFilePath(testCaseNumber);

            TextReader inputStream = new StreamReader(inputFilePath);
            var        cin         = new ConsoleInput(inputStream);

            var debugConsoleWriter = new DebugConsole();

            new Program(cin, debugConsoleWriter).Solve();

            var output = debugConsoleWriter.GetAllOutput();

            TextReader outputStream = new StreamReader(outputFilePath);
            var        outputAnswer = outputStream.ReadToEnd();

            Dbg.WriteLine(output);
            Dbg.WriteLine(outputAnswer);

            var isCorrect = output == outputAnswer;

            return isCorrect;
        }

        public void TestProblems(int targetTestCaseNumber = -1)
        {
            if (targetTestCaseNumber >= 0)
            {
                Console.WriteLine($"!!!!!!!!!!!! Check TestCase {targetTestCaseNumber} !!!!!!!!!!");
            }

            bool isSuccessAll = true;

            int testCaseNumber = 0;
            while (true)
            {
                testCaseNumber++;

                bool foundTargetTest = targetTestCaseNumber == testCaseNumber;

                if (targetTestCaseNumber >= 0 && !foundTargetTest)
                {
                    continue;
                }

                var inputFileName = GetInputFilePath(testCaseNumber);
                if (!File.Exists(inputFileName))
                {
                    break;
                }

                Console.WriteLine($"TestCase {testCaseNumber} =====================================================");

                var result = TestProblem(testCaseNumber);

                if (result)
                {
                    Console.WriteLine("Success");
                }
                else
                {
                    isSuccessAll = false;
                    Console.WriteLine("Failure *****");
                }

                if (foundTargetTest)
                {
                    break;
                }
            }

            if (isSuccessAll)
            {
                Console.WriteLine("!!!!!!!!! All Success !!!!!!!!!");
            }
        }
    }

#endif

    public static class Dbg
    {
        [Conditional("UTAKA_DEBUG")]
        public static void WriteLine(string str)
        {
            Console.WriteLine(str);
        }

        [Conditional("UTAKA_DEBUG")]
        public static void WriteLine()
        {
            Console.WriteLine();
        }

        [Conditional("UTAKA_DEBUG")]
        public static void Write(string str)
        {
            Console.Write(str);
        }
    }
}


Measured memory_bytes: 47636