#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using VI = vector<ll>;
using VV = vector<VI>;

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; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i,b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<'\n'
#define p2(s, t) cout << (s) << " " << (t) << '\n'
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << '\n'
#define SZ(x) ((int)(x).size())
#define SORT(A) sort(ALL(A))
#define RSORT(A) sort(ALL(A), greater<ll>())

const ll mod = 1e9 + 7;
const ll inf = 1e18;

struct UnionFind{
    vector<ll> parent;
    UnionFind(ll sz){
        parent.resize(sz);
        reset();
    }

    void reset(){
        FOR(i, 0, parent.size()){
            parent[i] = i;
        }
    }

    void unite(ll a, ll b){
        if(a>b){
            swap(a, b);
        }
        ll rootA = findRoot(a);
        ll rootB = findRoot(b);
        if(rootA>rootB){
            swap(rootA, rootB);
        }
        if(rootA==rootB){
            return;
        }else{
            // 小さい方を親にする
            parent[rootB] = rootA;
        }
    }

    ll findRoot(ll a){
        if(parent[a]==a){
            return a;
        }else{
            return parent[a] = findRoot(parent[a]);
        }
    }

    map<ll, vector<ll> > getGroups(){
        map<ll, vector<ll> > G;
        FOR(i, 0, SZ(parent)){
            ll r = findRoot(i);
            G[r].push_back(i);
        }
        return G;
    }

    bool is_same_group(ll a, ll b){
        ll rootA = findRoot(a);
        ll rootB = findRoot(b);
        if(rootA==rootB){
            return true;
        }else{
            return false;
        }
    }
};

struct Point{
    ll x;
    ll y;
    ll id;
    Point(ll x, ll y, ll id): x(x), y(y), id(id) {}
    static bool sortByX(Point a, Point b){
        if(a.x == b.x){
            return a.y < b.y;
        }else{
            return a.x < b.x;
        }
    }
    static bool sortByY(Point a, Point b){
        if(a.y == b.y){
            return a.x < b.x;
        }else{
            return a.y < b.y;
        }
    }
};

struct Edge{
    ll from;
    ll to;
    ll cost;
    Edge(ll f, ll t, ll c){
      from = f;
      to = t;
      cost = c;
    }
    static bool sortByCost(Edge a, Edge b){
        return a.cost < b.cost;
    }
};

ll MST(vector<Edge>& edges){
  ll N = edges.size();
  UnionFind uf(N);
  sort(ALL(edges), Edge::sortByCost);
  ll sum = 0;
  for(auto edge : edges){
    if(uf.findRoot(edge.from) == uf.findRoot(edge.to)) continue;
    uf.unite(edge.from, edge.to);
    sum += edge.cost;
  }
  return sum;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll N; 
    cin >> N;

    vector<Point> P;
    rep(i, N){
      ll x, y; cin >> x >> y;
      P.push_back(Point(x, y, i));
    }

    vector<Edge> edges;

    // 辺をはる
    sort(ALL(P), Point::sortByX);
    rep(i, N-1){
      ll dist = P[i+1].x - P[i].x;
      ll id0 = P[i].id;
      ll id1 = P[i+1].id;
      edges.push_back(Edge(id0, id1, dist));
      edges.push_back(Edge(id1, id0, dist));
    }

    // 辺をはる
    sort(ALL(P), Point::sortByY);
    rep(i, N-1){
      ll dist = P[i+1].y - P[i].y;
      ll id0 = P[i].id;
      ll id1 = P[i+1].id;
      edges.push_back(Edge(id0, id1, dist));
      edges.push_back(Edge(id1, id0, dist));
    }

    ll ans = MST(edges);
    p(ans);

    return 0;
}

Measured memory_bytes: 17644