#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif
using namespace std;

typedef long long ll;
//typedef pair<int,int> Pint;
typedef pair<ll, ll> P;
//typedef pair<int, pair<int, int>> P;
//typedef tuple<int,int,int> T;
typedef vector<ll> vec;
typedef vector<vec> mat;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define revrep(i, n) for(ll i = n-1; i >= 0; i--)
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll Mypow(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2) res *= x;
    x *= x;
    k /= 2;
  }
  return res;
}

ll INFL = 1000000000000000010;//10^18 = 2^60
int INF = 1000000000;//10^9
ll MOD  = 1000000007;
//vector<int> dy = {0,0,1,-1};
//vector<int> dx = {1,-1,0,0};

const int MAX_V = 200010;

int par[MAX_V];
int Rank[MAX_V];

void init_union_find(int n){
    for(int i = 0; i < n; i++){
        par[i] = i;
        Rank[i] = 1;
    }
}

int find(int x){
    if(par[x] == x) return x;
    else{
        return par[x] = find(par[x]);
    }
}

bool same(int x, int y){
    return find(x) == find(y);
}

void unite(int x, int y){
    int rx = find(x), ry = find(y);
    if(rx != ry){
        if(Rank[rx] >= Rank[ry]){
            par[ry] = rx;
            if(Rank[rx] == Rank[ry]) Rank[rx]++;
        }else{
            par[rx] = ry;
        }
    }
}


struct edge{int u, v, cost;};

bool comp(const edge& e1, const edge& e2){
  return e1.cost < e2.cost;
}

edge es[200010];
int V, E;

ll kruskal(){
  sort(es, es + E, comp);
  init_union_find(V);
  ll res = 0;
  rep(i, E){
    edge e = es[i];
    if(!same(e.u, e.v)){
      unite(e.u, e.v);
      res += e.cost;
    }
  }
  return res;
}

int main(){
  int N; cin >> N;
  vector<int> x(N), y(N);
  rep(i, N) cin >> x[i] >> y[i];
  vector<pair<int, int>> xlist(N);
  vector<pair<int, int>> ylist(N);
  rep(i, N){
    xlist[i] = {x[i], i};
    ylist[i] = {y[i], i};
  }
  sort(xlist.begin(), xlist.end());
  sort(ylist.begin(), ylist.end());
  vector<edge> xs(2 * (N - 1));
  int cnt = 0;
  rep(i, N-1){
    es[cnt++] = (edge){xlist[i].second, xlist[i+1].second, xlist[i+1].first - xlist[i].first};
    es[cnt++] = (edge){ylist[i].second, ylist[i+1].second, ylist[i+1].first - ylist[i].first};
  }
  V = N, E = xs.size();
  cout << kruskal() << endl;
}


Measured memory_bytes: 8064