using System;
using System.Collections.Generic;
using System.Linq;
using BitArray = System.Collections.BitArray;
using BigInteger = System.Numerics.BigInteger;
using TextReader = System.IO.TextReader;
using System.Text;

namespace AtCoderProject
{
    public class Program
    {
        public object Calc()
        {
            var N = consoleReader.Int;
            var towns = consoleReader.Repeat(N).Select(cr => new Point(cr.Split.Int)).ToArray();
            var townX = towns.Select((p, i) => Tuple.Create(p, i)).OrderBy(t => t.Item1.x).Select(t => t.Item2).ToArray();
            var townY = towns.Select((p, i) => Tuple.Create(p, i)).OrderBy(t => t.Item1.y).Select(t => t.Item2).ToArray();
            var roads = new List<Road>(2 * N);
            long cost = 0;
            for (int i = 1; i < N; i++)
            {
                roads.Add(new Road { a = townX[i - 1], b = townX[i], cost = towns[townX[i]].x - towns[townX[i - 1]].x });
                roads.Add(new Road { a = townY[i - 1], b = townY[i], cost = towns[townY[i]].y - towns[townY[i - 1]].y });
            }
            roads.Sort();

            var uf = new UnionFind(N);
            foreach (var r in roads)
            {
                if (uf.IsSameSet(r.a, r.b)) continue;
                uf.UnionSet(r.a, r.b);
                cost += r.cost;
            }

            return cost;
        }
        struct Road : IComparable<Road>
        {
            public int cost;
            public int a;
            public int b;

            public int CompareTo(Road other) => this.cost.CompareTo(other.cost);
        }
        struct Point : IEquatable<Point>
        {
            public int x;
            public int y;
            public Point(int[] arr) : this(arr[0], arr[1]) { }
            public Point(int x, int y)
            {
                this.x = x;
                this.y = y;
            }
            public bool Equals(Point other) => this.x == other.x && this.y == other.y;
            public override bool Equals(object obj)
            {
                if (obj is Point) return Equals((Point)obj);
                return false;
            }
            public override int GetHashCode() => x ^ y;
            public override string ToString() => $"({x}, {y})";
        }

        class UnionFind
        {
            int[] data;
            public UnionFind(int size)
            {
                this.data = Enumerable.Repeat(-1, size).ToArray();
            }

            public int Root(int x)
            {
                if (data[x] < 0) return x;
                return data[x] = Root(data[x]);
            }
            public int Count(int x) => -data[Root(x)];
            public void UnionSet(int x, int y)
            {
                var xRoot = Root(x);
                var yRoot = Root(y);
                if (xRoot == yRoot) return;
                else if (data[yRoot] < data[xRoot])//y側の方が多い場合は逆にする
                {
                    var tmp = yRoot;
                    yRoot = xRoot;
                    xRoot = tmp;
                }
                data[xRoot] += data[yRoot];
                data[yRoot] = xRoot;
            }
            public bool IsSameSet(int x, int y) => Root(x) == Root(y);
        }


        #region いつもの
#pragma warning disable
        private ConsoleReader consoleReader;
        public Program(ConsoleReader consoleReader) { this.consoleReader = consoleReader; }
        static void Main() => Console.WriteLine(new Program(new ConsoleReader(Console.In)).Calc()); static string AllLines<T>(IEnumerable<T> source) => string.Join("\n", source);
    }
    static class Ext
    {
        public static Dictionary<TKey, int> GroupCount<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) => source.GroupBy(keySelector).ToDictionary(g => g.Key, g => g.Count());
        public static Dictionary<TKey, int> GroupCount<TKey>(this IEnumerable<TKey> source) => source.GroupCount(i => i);
    }
    public class ConsoleReader { private string[] ReadLineSplit() => textReader.ReadLine().Split(Array.Empty<char>(), StringSplitOptions.RemoveEmptyEntries); private string[] line = Array.Empty<string>(); private int linePosition; private TextReader textReader; public ConsoleReader(TextReader tr) { textReader = tr; } public int Int => int.Parse(String); public long Long => long.Parse(String); public double Double => double.Parse(String); public string String { get { if (linePosition >= line.Length) { linePosition = 0; line = ReadLineSplit(); } return line[linePosition++]; } } public class SplitLine { private string[] splited; public SplitLine(ConsoleReader cr) { splited = cr.ReadLineSplit(); cr.line = Array.Empty<string>(); } public int[] Int => String.Select(x => int.Parse(x)).ToArray(); public int[] Int0 => String.Select(x => int.Parse(x) - 1).ToArray(); public long[] Long => String.Select(x => long.Parse(x)).ToArray(); public double[] Double => String.Select(x => double.Parse(x)).ToArray(); public string[] String => splited; } public SplitLine Split => new SplitLine(this); public class RepeatReader : IEnumerable<ConsoleReader> { ConsoleReader cr; int count; public RepeatReader(ConsoleReader cr, int count) { this.cr = cr; this.count = count; } public IEnumerator<ConsoleReader> GetEnumerator() => Enumerable.Repeat(cr, count).GetEnumerator(); System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => GetEnumerator(); public IEnumerable<string> String => this.Select(cr => cr.String); public IEnumerable<int> Int => this.Select(cr => cr.Int); public IEnumerable<int> Int0 => this.Select(cr => cr.Int - 1); public IEnumerable<long> Long => this.Select(cr => cr.Long); public IEnumerable<double> Double => this.Select(cr => cr.Double); } public RepeatReader Repeat(int count) => new RepeatReader(this, count); }
    #endregion
}


Measured memory_bytes: 37044