// #define STOPIT
#include <bits/stdc++.h>
#define loop(n) for (int ngtkana_is_a_genius = 0; ngtkana_is_a_genius < int(n); ngtkana_is_a_genius++)
#define rep(i, begin, end) for (int i = int(begin); (i) < int(end); i++)
#define all(v) v.begin(), v.end()
#define rand(l, r) std::uniform_int_distribution<>(l, r)(mt)
using lint = long long;
auto mt = std::mt19937_64(std::random_device{}());
auto cmn = [](auto& a, auto b){ if (a > b) {a = b; return true;} return false; };
auto cmx = [](auto& a, auto b){ if (a < b) {a = b; return true;} return false; };
void debug_impl() { std::cerr << std::endl; }
template <typename Head, typename... Tail>
void debug_impl(Head head, Tail... tail) { std::cerr << " " << head; debug_impl(tail...); }
#ifndef STOPIT
#define debug(...)\
  do {\
    std::cerr << std::boolalpha << "[" << #__VA_ARGS__ << "]:";\
    debug_impl(__VA_ARGS__);\
    std::cerr << std::noboolalpha;\
  } while (false)
#else
#define debug(...) {}
#endif

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr>
std::istream& operator>> (std::istream& is, Container& v)
  { for (auto & x : v) { is >> x; } return is; }

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr >
std::ostream& operator<< (std::ostream& os, Container const& v) {
 os << "{";
  for (auto it = v.begin(); it != v.end(); it++)
    {os << (it != v.begin() ? "," : "") << *it;}
  return os << "}";
}

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& tuple_input_impl(std::istream& os, Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
  { (void)std::initializer_list<int>{((void)(os >> std::get< Inds >(tuple)), 0)...}; return os; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& operator>> (std::istream& os, Tuple<Args...>& tuple)
  { return tuple_input_impl(os, tuple, std::index_sequence_for<Args...>()); }

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& tuple_output_impl(std::ostream& os, const Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
  { os << "("; (void)std::initializer_list<int>{((void)(os << (Inds > 0 ? "," : "") << std::get< Inds >(tuple)), 0)...}; return os << ")"; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& operator<< (std::ostream& os, const Tuple<Args...>& tuple)
 { return tuple_output_impl(os, tuple, std::index_sequence_for<Args...>()); }

class union_find {
    int n;
    std::vector<int> prt;

  public:
    union_find (int n) : n(n), prt(n, -1){}

    bool is_root (int x)        const {return prt.at(x) < 0;}
    int  size    (int x)        const {return -prt.at(find(x));}
    bool same(int x, int y)     const {return find(x) == find(y);}
    int  find    (int x)        const {
      while (!is_root(x)) x = prt.at(x);
      return x;
    }
    // Returns `true` if x and y are newly connected.
    // The smaller one x becomes a child of the larger one y.
    bool unite   (int x, int y) {
      if ((x = find(x)) == (y = find(y))) return false;
      if (size(x) > size(y)) std::swap(x, y);
      prt.at(y) += prt.at(x);
      prt.at(x) = y;
      return true;
    }
};

int main() {
  std::cin.tie(0); std::cin.sync_with_stdio(false);
  int n; std::cin >> n;
  std::vector<std::tuple<lint,lint,lint>> pts;
  rep(i,0,n) {
    lint x, y; std::cin >> x >> y;
    pts.emplace_back(x,y,i);
  }

  std::vector<std::tuple<lint,lint,lint>> edges;
  loop(2) {
    std::sort(all(pts));
    rep(t,0,n-1) {
      auto&& prv = pts.at(t);
      auto&& crr = pts.at(t+1);
      lint x0,y0,i0; std::tie(x0,y0,i0) = prv;
      lint x1,y1,i1; std::tie(x1,y1,i1) = crr;
      lint dx = x1 - x0;
      assert(0 <= dx);
      edges.emplace_back(dx,i0,i1);
    }

    for (auto&& tuple : pts) {
      lint x,y,i; std::tie(x,y,i) = tuple;
      tuple = std::make_tuple(y,x,i);
    }
  }

  std::sort(all(edges));
  // debug(edges);
  union_find uf(n);
  lint ans = 0;
  for (auto&& e : edges) {
    lint d,u,v; std::tie(d,u,v) = e;
    if (uf.unite(u,v)) ans += d;
  }
  std::cout << ans << std::endl;
  return 0;
}

Measured memory_bytes: 10864