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

#define rep(i,s,n) for (int i = (int)s; i < (int)n; i++)
#define ll long long
#define ld long double
#define pb push_back
#define eb emplace_back
#define All(x) x.begin(), x.end()
#define Range(x, i, j) x.begin() + i, x.begin() + j
#define lbidx(x, y) lower_bound(x.begin(), x.end(), y) - x.begin()
#define ubidx(x, y) upper_bound(x.begin(), x.end(), y) - x.begin()
#define llbidx(x, y, z) lower_bound(x.begin(), x.end(), z) - lower_bound(x.begin(), x.end(), y) // 二要素間の距離
#define deg2rad(deg) ((((double)deg)/((double)360)*2*M_PI))
#define rad2deg(rad) ((((double)rad)/(double)2/M_PI)*(double)360)
#define Find(set, element) set.find(element) != set.end()
#define Decimal(x) printf("%.10f\n", x) // 小数点を10桁まで表示
// debug用
#define PrintVec(x) for (auto elementPrintVec: x) { cout << elementPrintVec << " "; } cout << "\n";
#define debug(x) cerr << #x << ": " << (x) << "\n";
#define endl "\n"
// gcj print用
#define Case(x) printf("Case #%d: ", x);

typedef pair<int, int> PI;
typedef pair<ll, ll> PLL;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<vector<vector<int>>> vvvi;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef vector<vector<vector<int>>> vvvl;
typedef vector<PI> vpi;
typedef vector<vector<PI>> vvpi;
typedef vector<vector<vector<PI>>> vvvpi;
typedef vector<PLL> vpl;
typedef vector<vector<PLL>> vvpl;
typedef vector<vector<vector<PLL>>> vvvpl;

int POWINT(int x, int n) {
  int ret = 1;
  while (n > 0) {
    if (n & 1) ret *= x;
    x *= x;
    n >>= 1;
  }
  return ret;
};

ll POWLL(ll x, int n) {
  ll ret = 1;
  while (n > 0) {
    if (n & 1) ret *= x;
    x *= x;
    n >>= 1;
  }
  return ret;
};

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

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

void print() {
  cout << endl;
}

template <class T>
void print(vector<T> &vec) {
  for (auto& a : vec) {
    cout << a;
    if (&a != &vec.back()) cout << " ";
  }
  cout << endl;
}

template <class T>
void print(vector<T> &vec, ll k){
   ll n = vec.size();
   k = min(k, n);
   rep(i, 0, k-1) cout << vec[i] << " ";
   cout << vec[k-1] << endl;
}

template <class T>
void print(vector<vector<T>> &df) {
  for (auto& vec : df) {
    print(vec);
  }
}

template<class T, class U>
void print(pair<T,U> &p){
  cout << p.first << " " << p.second << "\n";
}

class Unionfind {
public:
  int N;
  vector<int> par; // 節点
  vector<int> rank; // 木の高さ
  vector<int> size; // 節点が属する木の節点数
  int treeNum; // 木の数
  Unionfind(int N) : par(N), rank(N, 0), size(N, 1) {
    for (int i = 0; i < N; i++) {
      par[i] = i;
    }
    treeNum = N;
  }
  // 節点(木)追加
  void addNode(int x) {
    par[x] = x;
    rank[x] = 0;
    size[x] = 1;
    treeNum++;
  }
  // 根を探すと同時に経路上にある節点の親が根になるように代入
  int root(int x) {
    return par[x] == x ? x : par[x] = root(par[x]);
  }
  // 同じ木に属しているか
  bool same(int x, int y) {
    return root(x) == root(y);
  }
  // rankが低い方の木をrankが高い方の木の根に結びつける(結びつけた後の新しい木の高さが高くなることがないため)
  void unite(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y) {
      return;
    }
    treeNum--;
    if (rank[x] < rank[y]) {
      par[x] = y;
      size[y] += size[x];
    } else {
      par[y] = x;
      size[x] += size[y];
      if (rank[x] == rank[y]) {
        rank[x] += 1;
      }
    }
  }

  vector<vector<int>> group() { // 二重ループだが実はO(N)
    vector<vector<int>> res; // 実はresの全体のサイズはN
    vector<bool> fixed(N, false);
    for (int i = 0; i < N; i++) {
      if (!fixed[i]) {
        vector<int> tmp;
        for (int j = i; j < N; j++) {
          if (same(i, j)) {
            tmp.push_back(j);
            fixed[j] = true;
          }
        }
        res.push_back(tmp);
      }
    }

    return res;
  }
};

struct TOWN {
  int id;
  ll x, y;
  TOWN() {}
  TOWN(int id, ll x, ll y): id(id), x(x), y(y) {}
};

bool lessX(const TOWN &t1, const TOWN &t2) { return t1.x < t2.x; };
bool lessY(const TOWN &t1, const TOWN &t2) { return t1.y < t2.y; };


class LOAD {
public:
  int t1, t2;
  ll cost;
  LOAD() {}
  LOAD(int t1, int t2, ll cost): t1(t1), t2(t2), cost(cost) {}
  bool operator < (const LOAD &l) const {
    return cost > l.cost;
  }
};


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

  int n;
  cin >> n;

  vector<TOWN> tx(n), ty(n);

  rep(i, 0, n) {
    ll x, y;
    cin >> x >> y;
    tx[i] = ty[i] = TOWN(i, x, y);
  }

  sort(All(tx), lessX);
  sort(All(ty), lessY);

  priority_queue<LOAD> pq;

  rep(i, 0, n-1) {
    ll costx = abs(tx[i+1].x - tx[i].x);
    ll costy = abs(ty[i+1].y - ty[i].y);
    LOAD loadx(tx[i+1].id, tx[i].id, costx), loady(ty[i+1].id, ty[i].id, costy);
    pq.push(loadx);
    pq.push(loady);
  }

  Unionfind uf(n);
  ll ans = 0;
  while (!pq.empty()) {
    auto load = pq.top(); pq.pop();
    int id1 = load.t1, id2 = load.t2;
    if (uf.same(id1, id2)) continue;

    uf.unite(id1, id2);
    ans += load.cost;
  }

  cout << ans << endl;




  return 0;
};


Measured memory_bytes: 11120