// Original C++ solution (slower):
/*************************************************

 *************************************************

 *************************************************

 *** _________________  |            |  |     /***

 ***         |          |            |  |    / ***

 ***         |          |            |  |   /  ***

 ***         |          |            |  |  /   ***

 ***         |          |            |  | /    ***

 ***         |          |____________|  |/  en ***

 ***         |          |            |  |\     ***

 ***         |          |            |  | \    ***

 *** _____   |          |            |  |  \   ***

 ***   |     |          |            |  |   \  ***

 ***   \     /          |            |  |    \ ***

 ***    \___/           |            |  |     \***

 *************************************************

 *************Written by: JiangHaoKai*************

 *************************************************/



//#include <bits/stdc++.h>

#include <cassert>

#include <cctype>

#include <cerrno>

#include <cfloat>

#include <climits>

#include <clocale>

#include <cmath>

#include <csetjmp>

#include <csignal>

#include <cstdarg>

#include <cstddef>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <ctime>

#include <ccomplex>

#include <cfenv>

#include <cinttypes>

#include <cstdalign>

#include <cstdbool>

#include <cstdint>

#include <ctgmath>

#include <cwchar>

#include <cwctype>

#include <algorithm>

#include <bitset>

#include <complex>

#include <deque>

#include <fstream>

#include <functional>

#include <iomanip>

#include <iostream>

#include <limits>

#include <list>

#include <locale>

#include <map>

#include <memory>

#include <numeric>

#include <queue>

#include <set>

#include <sstream>

#include <stack>

#include <stdexcept>

#include <string>

#include <typeinfo>

#include <valarray>

#include <vector>

#include <array>

#include <atomic>

#include <chrono>

#include <condition_variable>

#include <forward_list>

#include <future>

#include <mutex>

#include <random>

#include <ratio>

#include <regex>

#include <scoped_allocator>

#include <system_error>

#include <thread>

#include <tuple>

#include <typeindex>

#include <unordered_map>

#include <unordered_set>

//#include <windows.h>

using namespace std;



typedef long long ll;

typedef unsigned int ui;

typedef unsigned long long ull;

typedef float fl;

typedef double ld;

typedef pair<int,int> pii;

#define ui(n) ((unsigned int)(n))

#define ll(n) ((long long)(n))

#define ull(n) ((unsigned long long)(n))

#define fl(n) ((float)(n))

#define ld(n) ((double)(n))

#define char(n) ((char)(n))

#define Bool(n) ((bool)(n))

#define fixpoint(n) fixed<<setprecision(n)

const int INF=1e9+7;

const ll LINF=1e18;

#define PI 3.1415926535897932384626433832795028841971

#define MP make_pair

#define MT make_tuple

#define All(a) (a).begin(),(a).end()

#define pall(a) (a).rbegin(),(a).rend()

#define mod 1000000007

#define sz(a) ((int)(a).size())

#define rep(i,n) for(int i=0;i<n;i++)

#define rep1(i,n) for(int i=1;i<=n;i++)

#define repa(i,a,n) for(int i=a;i<n;i++)

#define repd(i,n) for(int i=n-1;i>=0;i--)

#define FOR(i,a,n,step) for(int i=a;i<n;i+=step)

#define repv(itr,v) for(__typeof((v).begin()) itr=(v).begin();itr!=(v).end();itr++)

#define repV(i,v) for(auto i:v)

#define repE(i,v) for(auto &i:v)

#define MS(x,y) memset(x,y,sizeof(x))

#define sqr(x) ((x)*(x))

#define filein(x) freopen(x,"r",stdin)

#define fileout(x) freopen(x,"w",stdout)

#define fileout2(filename,name) ofstream name(filename,ios::out)

#define filein2(filename,name) ifstream name(filename,ios::in)

#define file(filename,name) fstream name(filename,ios::in|ios::out)

#define Pause system("pause")

#define Cls system("cls")

#define fs first

#define sc second

#define PC(x) putchar(x)

#define GC(x) x=getchar()

#define Endl PC('\n')



inline int READ()

{

    int X=0,w=0;char ch=0;while(!isdigit(ch)){w|=ch=='-';ch=getchar();}while(isdigit(ch))X=(X<<3)+(X<<1)+(ch^48),ch=getchar();

	return w?-X:X;

}

inline void WRITE(int x){if(x<0)putchar('-'),x=-x;if(x>9)WRITE(x/10);putchar(x%10+'0');}

inline void WRITEend(int x){WRITE(x);exit(0);}



inline ll powmod(ll a,ll b){ll res=1;a%=mod;assert(b>=0);for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}

inline ll gcdll(ll a,ll b){return b?gcdll(b,a%b):a;}

inline string itoa(ll a){string res="";while(a>0)res+=(a%10+'0'),a/=10;reverse(All(res));return res==""?"0":res;}

inline ll atoi(string s){ll res=0;repV(i,s)res=res*10+i-'0';return res;}

const int dx[]={0,1,0,-1,1,-1,-1,1};

const int dy[]={1,0,-1,0,-1,-1,1,1};

/**************************************************************Begin***************************************************************/

int n=READ(),a[100010][2],par[100010],u[100010];

ll ans;

vector<pair<ll,pair<int,int> > > v;



inline int FIND(int x)

{

	return x==par[x]?x:par[x]=FIND(par[x]);

}



inline bool cmp1(int x,int y)

{

	return a[x][0]<a[y][0];

}



inline bool cmp2(int x,int y)

{

	return a[x][1]<a[y][1];

}



int main()

{

	rep1(i,n) a[i][0]=READ(),a[i][1]=READ();

	

	rep1(i,n) u[i]=par[i]=i;

	

	sort(u+1,u+n+1,cmp1);

	rep1(i,n-1) v.push_back(MP(a[u[i+1]][0]-a[u[i]][0],MP(u[i],u[i+1])));

	

	sort(u+1,u+n+1,cmp2);

	rep1(i,n-1) v.push_back(MP(a[u[i+1]][1]-a[u[i]][1],MP(u[i],u[i+1])));

	

	sort(All(v));

	repV(i,v)

	{

		if(FIND(i.sc.fs)==FIND(i.sc.sc)) continue;

		ans+=i.fs;

		par[FIND(i.sc.fs)]=FIND(i.sc.sc);

	}

	

	printf("%lld",ans);



	return 0;

}

/***************************************************************End****************************************************************/


// Optimized solution to the same problem (faster):
#include <stdio.h>

#include <stdlib.h>

#include <algorithm>



// 全局变量

const int N = 100010 , M = N + N;

int x[N],y[N],id[N],n;



typedef struct ufset *UFset;

struct ufset

{

  int *parent;

  int *root;

};

UFset UFinit(int size)

{

  int e;

  UFset U=(UFset)malloc(sizeof *U);

  U->parent=(int*)malloc((size+1)*sizeof(int));

  U->root=(int*)malloc((size+1)*sizeof(int));

  for(e=1; e<=size; e++)

  {

    U->parent[e]=1;

    U->root[e]=1;

  }

  return U;

}

int UFfind(int e,UFset U)

{

  int i,j = e;

  while(!U->root[j]) j = U->parent[j];

  while(j!=e){

    i = U->parent[e];

    U->parent[e]=j;

    e=i;

  }

  return j;

}

int UFunion(int i,int j,UFset U)

{

  if(U->parent[i]<U->parent[j])

  {

    U->parent[j]+=U->parent[i];

    U->root[i]=0;

    U->parent[i]=j;

    return j;

  }

  else

  {

    U->parent[i]+=U->parent[j];

    U->root[j]=0;

    U->parent[j]=i;

    return i;

  }

}



// 记录优化后的边集数

struct Edge

{

  int u, v, cost;

  bool operator <(const Edge&b) const

  {

    return cost < b.cost;

  }

} edge[M];

int tot;

// 按照X轴排序

bool cmpX(int a, int b)

{

  return x[a] < x[b];

}

// 按照Y轴排序

bool cmpY(int a, int b)

{

  return y[a] < y[b];

}

void add(int c, int a, int b)

{

  edge[tot].cost = c;

  edge[tot].u = a;

  edge[tot++].v = b;

}

void Work()

{

    scanf("%d", &n);

  int i;

  for (i = 1; i <= n; ++i)

  {

    scanf("%d%d", x + i, y + i);

    id[i] = i;

  }

  std::sort(id + 1 , id + n + 1, cmpX);

  for (i = 2; i <= n; ++i)

    add(x[id[i]] - x[id[i - 1]], id[i], id[i - 1]);

  std::sort(id + 1 , id + n + 1, cmpY);

  for (i = 2; i <= n; ++i)

    add(y[id[i]] - y[id[i - 1]], id[i], id[i - 1]);

  UFset UFS = UFinit(n);



  // 按照花费排序

  std::sort(edge, edge + tot);

  long long totcost = 0;

  for (i = 0; i < tot; ++i)

  {

    int u = edge[i].u, v = edge[i].v;

    u = UFfind(u,UFS), v = UFfind(v,UFS);

    if (u != v)

    {

      UFunion(u,v,UFS);

      totcost += edge[i].cost;

    }

  }

  printf("%lld\n", totcost);

}

int main()

{

  Work();

  return 0;

}


// Fastest known solution for this problem: