#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit(b) (1ll << (b))
#define uniq(v) (v).erase(unique(all(v)), (v).end())

using namespace std;

using i32 = int;
using i64 = long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() { cout << "Yes" << '\n'; exit(0); }
inline void no() { cout << "No" << '\n'; exit(0); }
inline i64 gcd(i64 a, i64 b) { if (min(a, b) == 0) return max(a, b); if (a % b == 0) return b; return gcd(b, a % b); }
inline i64 lcm(i64 a, i64 b) { return a / gcd(a, b) * b; }
void solve(); int main() { ios::sync_with_stdio(0); cin.tie(0); cout << fixed << setprecision(16); solve(); return 0; }
template <typename T> class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T> class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) { if (x < y) x = y; }
template <typename T> inline void amin(T &x, T y) { if (x > y) x = y; }
template <typename T> inline T power(T x, i64 n, T e = 1) { T r = e; while (n > 0) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; }
template <typename T> istream& operator>>(istream &is, vector<T> &v) { each(x, v) is >> x; return is; }
template <typename T> ostream& operator<<(ostream &os, vector<T> &v) { rep(i, v.size()) { if (i) os << ' '; os << v[i]; } return os; }
template <typename T, typename S> istream& operator>>(istream &is, pair<T, S> &p) { is >> p.first >> p.second; return is; }
template <typename T, typename S> ostream& operator<<(ostream &os, pair<T, S> &p) { cout << p.first << ' ' << p.second; return os; }

struct UnionFind {
  vi32 par;
  vi32 siz;
  UnionFind(int n) {
    par = vi32(n);
    siz = vi32(n, 1);
    iota(all(par), 0);
  }
  int root(int x) {
    if (par[x] == x) return x;
    return par[x] = root(par[x]);
  }
  void unite(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y) return;
    par[x] = y;
    siz[y] += siz[x];
  }
  bool same(int x, int y) {
    return root(x) == root(y);
  }
  int size(int x) {
    return siz[root(x)];
  }
};

void solve() {
  int N; cin >> N;
  vi32 x(N), y(N);
  rep(i, N) cin >> x[i] >> y[i];

  pqasc<tuple<int, int, int>> pq;

  vi32 o(N);
  iota(all(o), 0);
  sort(all(o), [&](int i, int j) { return x[i] < x[j]; });
  rep(i, N - 1) {
    int c = abs(x[o[i + 1]] - x[o[i]]);
    pq.emplace(c, o[i], o[i + 1]);
  }
  sort(all(o), [&](int i, int j) { return y[i] < y[j]; });
  rep(i, N - 1) {
    int c = abs(y[o[i + 1]] - y[o[i]]);
    pq.emplace(c, o[i], o[i + 1]);
  }

  i64 ans = 0;

  auto uf = UnionFind(N);
  while (true) {
    int c, v, u;
    tie(c, v, u) = pq.top(), pq.pop();
    if (uf.same(v, u)) continue;
    uf.unite(v, u);
    ans += c;
    if (uf.size(v) == N) break;
  }

  cout << ans << '\n';
}


Measured memory_bytes: 6132