using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);
        Solve();
        Console.Out.Flush();
    }
    static void Solve()
    {
        var N = sc.ReadInt();
        var XY = new Tuple<long, long, int>[N];
        for (int i = 0; i < N; i++)
        {
            var x = sc.ReadLong();
            var y = sc.ReadLong();
            XY[i] = Tuple.Create(x, y, i);
        }
        var edges = new List<Tuple<int, int, long>>();
        Array.Sort(XY);
        for (int i = 0; i < N - 1; i++)
        {
            var s = XY[i].Item3;
            var sx = XY[i].Item1;
            var t = XY[i + 1].Item3;
            var tx = XY[i + 1].Item1;
            edges.Add(Tuple.Create(s, t, Math.Abs(sx - tx)));
            edges.Add(Tuple.Create(t, s, Math.Abs(sx - tx)));
        }
        Array.Sort(XY, (t1, t2) => -t1.Item2.CompareTo(t2.Item2));
        for (int i = 0; i < N - 1; i++)
        {
            var s = XY[i].Item3;
            var sy = XY[i].Item2;
            var t = XY[i + 1].Item3;
            var ty = XY[i + 1].Item2;
            edges.Add(Tuple.Create(s, t, Math.Abs(sy - ty)));
            edges.Add(Tuple.Create(t, s, Math.Abs(sy - ty)));
        }
        edges.Sort((e1, e2) => e1.Item3.CompareTo(e2.Item3));
        var uf = new UnionFind(N);
        var ans = 0L;
        foreach (var e in edges)
        {
            var s = e.Item1;
            var t = e.Item2;
            var cost = e.Item3;
            if (!uf.Same(s, t))
            {
                ans += cost;
                uf.Union(s, t);
            }
        }
        Console.WriteLine(ans);
    }

    class UnionFind
    {
        public int[] Parents;
        public int[] Rank;
        public UnionFind(int n)
        {
            this.Parents = Enumerable.Repeat(-1, n).ToArray();
            this.Rank = new int[n];
        }
        public int Find(int x)
        {
            if (this.Parents[x] < 0) return x;
            this.Parents[x] = Find(this.Parents[x]);
            return this.Parents[x];
        }
        public int Size(int x)
        {
            return -this.Parents[this.Find(x)];
        }
        public bool Same(int x, int y)
        {
            return this.Find(x) == this.Find(y);
        }
        public bool Union(int x, int y)
        {
            x = this.Find(x);
            y = this.Find(y);
            if (x == y) return false;

            if (this.Rank[x] < this.Rank[y])
            {
                var tmp = x;
                x = y;
                y = tmp;
            }
            if (this.Rank[x] == this.Rank[y]) this.Rank[x]++;
            this.Parents[x] += this.Parents[y];
            this.Parents[y] = x;
            return true;
        }
        public int GetGroupCount()
        {
            return this.Parents.Count(p => p < 0);
        }
    }
    static Scanner sc = new Scanner();
}
class Scanner
{
    string[] S = new string[0];
    int Index = 0;
    char[] Separators = new char[] { ' ' };

    public string Next()
    {
        if (this.Index < this.S.Length) return this.S[this.Index++];
        var line = "";
        while (line == "") line = Console.ReadLine();
        this.S = line.Split(this.Separators, StringSplitOptions.RemoveEmptyEntries);
        if (this.S.Length == 0) return this.Next();
        this.Index = 0;
        return this.S[this.Index++];
    }
    public string ReadStr()
    {
        return this.Next();
    }
    public char ReadChar()
    {
        return this.Next()[0];
    }
    public int ReadInt()
    {
        return int.Parse(this.Next());
    }
    public uint ReadUInt()
    {
        return uint.Parse(this.Next());
    }
    public long ReadLong()
    {
        return long.Parse(this.Next());
    }
    public double ReadDouble()
    {
        return double.Parse(this.Next());
    }
    public Tuple<int, int> ReadTup(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<long, long> ReadTupLong(int add = 0)
    {
        return Tuple.Create(this.ReadLong() + add, this.ReadLong() + add);
    }
    public Tuple<int, int, int> ReadTup3(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<int, int, int, int> ReadTup4(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public int[] ReadIntArray(int n)
    {
        var array = new int[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadInt();
        }
        return array;
    }
    public long[] ReadLongArray(int n)
    {
        var array = new long[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadLong();
        }
        return array;
    }
    public double[] ReadDoubleArray(int n)
    {
        var array = new double[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadDouble();
        }
        return array;
    }
    public char[] ReadCharArray(int n)
    {
        var array = new char[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadChar();
        }
        return array;
    }
    public string[] ReadStrArray(int n)
    {
        var array = new string[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadStr();
        }
        return array;
    }
    public Tuple<long, long>[] ReadTupLongArray(int n, int add = 0)
    {
        var array = new Tuple<long, long>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTupLong(add);
        }
        return array;
    }
    public Tuple<int, int>[] ReadTupArray(int n, int add = 0)
    {
        var array = new Tuple<int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup(add);
        }
        return array;
    }
    public Tuple<int, int, int>[] ReadTup3Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup3(add);
        }
        return array;
    }
    public Tuple<int, int, int, int>[] ReadTup4Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup4(add);
        }
        return array;
    }
}


Measured memory_bytes: 44468