#include <iostream>
#include <algorithm>
#include <utility>
#include <string>
#include <vector>
#include <set>
#include <stack>
#include <queue>
#include <map>
#include <math.h>
#include <string.h>
#include <iomanip>
#include <numeric>
#include <cstdlib>
#include <cstdint>
#include <cmath>
#include <functional>
#include <limits>
#include <cassert>
#include <bitset>

using namespace std;

/* template */

using ll = long long;

void debug_out() { std::cout << std::endl; }
 
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cout << H << " ";
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cout << "debug: "; debug_out(__VA_ARGS__)
#else
#define debug(...) 
#endif

#define rep(i, a, n) for (int i = (int)(a); i < (int)(n); i++)
#define rrep(i, a, n) for (int i = ((int)(n-1)); i >= (int)(a); i--)
#define Rep(i, a, n) for (long long i = (long long)(a); i< (long long)(n); i++)
#define RRep(i, a, n) for (long long i = ((long long)(n-1ll)); i>=(long long)(a); i--)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()

template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}

struct Edge{
    int to;
    ll weight;
    Edge(int t, ll w) : to(t), weight(w){ }
};

struct edge{
    int from;
    int to;
    ll weight;
    edge(int f,int t,ll w) : from(f), to(t), weight(w){ }
};


using Graph = vector<vector<Edge>>;
using graph = vector<vector<int>>;
using edges = vector<edge>;

template <class T>
inline bool chmin(T &a, T b){
    if (a > b){
        a = b;
        return true;
    }
    return false;
}

template <class T>
inline bool chmax(T &a, T b){
    if (a < b){
        a = b;
        return true;
    }
    return false;
}

template <class T>
T lcm(T a, T b){
    return (a*b)/gcd(a,b);
}

ll ctoi(char c) {
	switch (c) {
	case '0': return 0; case '1': return 1; case '2': return 2;
	case '3': return 3; case '4': return 4; case '5': return 5;
	case '6': return 6; case '7': return 7; case '8': return 8;
	case '9': return 9;  default: return 0;
	}
}

constexpr ll LNF = 1LL<<50;

constexpr int INF = 1e9+7;

const long double PI=3.14159265358979323846;


vector<int> dx = {1,0,-1,1,-1,0};
vector<int> dy = {1,1,1,0,0,-1};

/* template */

struct UnionFind{
private:
    std::vector<int> par;

    int find(int x){
        if(par[x]<0) return x;
        else return par[x] = find(par[x]);
    }

public:
    UnionFind(int n=0): par(n,-1){ }

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

    bool unite(int x, int y){
        x = find(x); y = find(y);
        if(x==y) return false;
        if(par[x]>par[y]) std::swap(x,y);
        par[x]+=par[y];
        par[y] = x;
        return true;
    }

    int size(int x){
        return -par[find(x)];
    }

    int count_group(){
        int c = 0;
        for(int i = 0; i<par.size(); i++){
            if(par[i]<0) c++; 
        }
        return c;
    }
};

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    using pll = pair<ll,ll>;

    int n; cin >> n;
    vector<pair<ll,ll>> x(n);
    vector<pair<ll,ll>> y(n);
    map<int,pair<ll,ll>> m;
    rep(i,0,n){
        cin >> x[i].first;
        x[i].second = i;
        cin >> y[i].first;
        y[i].second = i;
        m[i] = make_pair(x[i].first,y[i].first);
    }
    sort(all(x));
    sort(all(y));
    priority_queue<pair<ll,pll> , vector<pair<ll,pll>> , greater<pair<ll,pll>>> que;
    rep(i,0,n-1){
        que.push(make_pair(x[i+1].first-x[i].first,pll(x[i+1].second,x[i].second)));
        que.push(make_pair(y[i+1].first-y[i].first,pll(y[i+1].second,y[i].second)));
    }
    UnionFind uf(n);
    ll ans = 0;
    while(!que.empty()){
        auto nxt = que.top();
        pll nx = nxt.second;
        que.pop();
        if(uf.same(nx.first,nx.second)){
            continue;
        }
        else{
            uf.unite(nx.first,nx.second);
            ans += nxt.first;
        }
    }
    cout << ans << endl;
}

Measured memory_bytes: 18884