#include <iostream>
#include <iomanip>
#include <string>
#include <stack>
#include <vector>
#include <math.h>
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <map>
#include <set>
#include <queue>
#include <list>
#include <regex>
using namespace std;
using pii  = pair<int,int>;
using ll=long long;
using ld=long double;
#define pb push_back
#define mp make_pair
#define sc second
#define fr first
#define stpr setprecision
#define cYES cout<<"YES"<<endl
#define cNO cout<<"NO"<<endl
#define cYes cout<<"Yes"<<endl
#define cNo cout<<"No"<<endl
#define rep(i,n) for(ll i=0;i<(n);++i)
#define Rep(i,a,b) for(ll i=(a);i<(b);++i)
#define rrep(i,n) for(int i=n-1;i>=0;i--)
#define rRep(i,a,b) for(int i=a;i>=b;i--)
#define crep(i) for(char i='a';i<='z';++i)
#define psortsecond(A,N) sort(A,A+N,[](const pii &a, const pii &b){return a.second<b.second;});
#define ALL(x) (x).begin(),(x).end()
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define endl '\n'
int ctoi(const char c){
  if('0' <= c && c <= '9') return (c-'0');
  return -1;
}
ll gcd(ll a,ll b){return (b == 0 ? a : gcd(b, a%b));}
ll lcm(ll a,ll b){return a*b/gcd(a,b);}
constexpr ll MOD=1000000007;
constexpr ll INF=1000000011;
constexpr ll MOD2=998244353;
constexpr ll LINF = 1001002003004005006ll;
constexpr ld EPS=10e-8;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename T> istream& operator>>(istream& is,vector<T>& v){for(auto&& x:v)is >> x;return is;}
template<typename T,typename U> istream& operator>>(istream& is, pair<T,U>& p){ is >> p.first; is >> p.second; return is;}
template<typename T,typename U> ostream& operator>>(ostream& os, const pair<T,U>& p){ os << p.first << ' ' << p.second; return os;}
template<class T> ostream& operator<<(ostream& os, vector<T>& v){
    for(auto i=begin(v); i != end(v); ++i){
        if(i !=begin(v)) os << ' ';
        os << *i;
    }
    return os;
}

class DisjointSet{
    public:
        vector<int> rank,p;

        DisjointSet(){}

        //初期化
        DisjointSet(int size){
            rank.resize(size,0);
            p.resize(size,0);
            rep(i,size){
                makeSet(i);
            }
        }        
        void makeSet(int x){
            p[x]=x;
            rank[x]=0;
        }

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

        void unite(int x,int y){
            link(findSet(x),findSet(y));
        }

        void link(int x,int y){
            if(rank[x]>rank[y]){
                p[y]=x;
            }
            else{
                p[x]=y;
                if(rank[x]==rank[y]){
                    rank[y]++;
                }
            }
        }

        int findSet(int x){
            if(x!=p[x]){
                p[x]=findSet(p[x]);
            }
            return  p[x];
        }
};

class Edge{
    public:
    ll  source,target,cost;
    Edge(ll source=0,ll  target=0,ll cost=0):
    source(source),target(target),cost(cost){}
    bool operator < (const Edge &e) const{
        return cost < e.cost;
    }
};

ll kruskal(ll N,vector<Edge> edges){
    ll totalCost = 0;
    sort(edges.begin(),edges.end());
    DisjointSet dset = DisjointSet(N+1);
    rep(i,N){
        dset.makeSet(i);
    }
    ll source,target;
    rep(i,edges.size()){
        Edge e = edges[i];
        if(!dset.same(e.source,e.target)){
            //MST.push_back(e);
            totalCost += e.cost;
            dset.unite(e.source,e.target);
        }
    }
    return totalCost;
}

int main(){
  ll N,x[100007],y[100007];
  pair<ll,pair<ll,ll>> cit[100007];
  cin >> N;
  vector<Edge> edges;
  rep(i,N){
    cin >> cit[i].fr >> cit[i].sc.fr ;
    cit[i].sc.sc = i;
  }
  sort(cit,cit+N);
  rep(i,N-1){
    edges.push_back(Edge(cit[i].sc.sc,cit[i+1].sc.sc,cit[i+1].fr-cit[i].fr));
  }
  rep(i,N){
    swap(cit[i].fr,cit[i].sc.fr);
  }
  sort(cit,cit+N);
  rep(i,N-1){
    edges.push_back(Edge(cit[i].sc.sc,cit[i+1].sc.sc,cit[i+1].fr-cit[i].fr));
  }
  cout << kruskal(N,edges) << endl;
}

Measured memory_bytes: 14060