#include "bits/stdc++.h"
using namespace std;


/* macro */
#define rep(i,a,b) for(int i=a;i<b;i++)
#define revrep(i,a,b) for(int i = a; i > b; i--)
#define int long long
#define exist(s,e) ((s).find(e)!=(s).end())
#define all(v) (v).begin(), (v).end()
#define each(s,itr) for(auto (itr) = s.begin(); (itr) != s.end(); (itr)++)
#define sum(v) accumulate(all(v), (0LL))


/* alias */
template<class T> using vec = vector<T>;
typedef vector<int> vi;
typedef pair<int, int> pi;


/* constant */
const int inf = pow(2, 62);
const int mod = 1000000007;
int dx[8]={1,0,-1,0,-1,1,-1,1};
int dy[8]={0,1,0,-1,-1,-1,1,1};

/* io_method */
int input(){int tmp;cin >> tmp;return tmp;}
string raw_input(){string tmp;cin >> tmp;return tmp;}
string readline(){string s;getline(cin, s);return s;}
template<class T> void printx(T n){cout << n;}
template<class T, class U> void printx(pair<T, U> p){cout << "(" << p.first << "," << p.second << ")";}
template<class T> void printx(vector<T> v){cout << "{";rep(i,0,v.size()){printx(v[i]);if(i != v.size()-1)printx(",");}cout << "}";}
template<class T> void print(T n){printx(n);cout << endl;}
template<class T> void print(set<T> s){cout << "{";each(s, e){if(e != s.begin()) printx(",");printx(*e);}cout << "}" << endl;}
template<class T, class U> void print(map<T, U> mp){cout << "{";each(mp, e){cout << "(" << e -> first << "," << e -> second << ")";}cout << "}" << endl;}


/* general_method */
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; }




/* main */
struct Union_Find{
    vector<int> par;
    vector<int> rank;

    Union_Find(int n){
        for(int i = 0; i < n; i++){
            par.push_back(i);
            rank.push_back(0);
        }
    }

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

    void merge(int x, int y){
        x = root(x);
        y = root(y);

        if(x == y) return;

        if(rank[x] < rank[y]){
            par[x] = y;
        }else{
            par[y] = x;
            if(rank[x] == rank[y]) rank[x]++;
        }
    }

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

};

signed main(){

    cin.tie(0);
    ios::sync_with_stdio(false);

    


    int n = input();

    vec<pi> sortx;
    vec<pi> sorty;

    int ans = 0;
    Union_Find uf = Union_Find(n);

    rep(i,0,n){
        int x, y; cin >> x >> y;
        sortx.push_back(make_pair(x, i));
        sorty.push_back(make_pair(y, i));
    }

    sort(all(sortx));
    sort(all(sorty));
    
    vec<vi> edges;
    
    rep(i,0,n-1){
        int f = sortx[i].second, t = sortx[i + 1].second, dist = sortx[i + 1].first - sortx[i].first;
        edges.push_back({dist, f, t});
    }

    rep(i,0,n-1){
        int f = sorty[i].second, t = sorty[i + 1].second, dist = sorty[i + 1].first - sorty[i].first;
        edges.push_back({dist, f, t});
    }

    sort(all(edges));


    for(auto e : edges){
        int dist = e[0], f = e[1], t = e[2];
        if(not uf.same(f, t)){
            ans += dist;
            uf.merge(f, t);
        }
    }

    print(ans);








    











   








    
    












    

    








    






    


    
    

    
    






    




    

    





    

   




    

    

    



    
    



    







    

    

    




    



    



    

 
    
    


    

    
   
    













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Measured memory_bytes: 17284