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

template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)

#define rep(i,n) for (int i = 0; i < n; ++i)
#define reps(i,s,n) for (int i = s; i < n; ++i)
#define rep1(i,n) for (int i = 1; i <= n; ++i)
#define per(i,n) for (int i = n - 1; i >= 0; --i)
#define per1(i,n) for (int i = n; i >= 1; --i)
#define all(c) begin(c),end(c)
template<typename T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<typename T> inline T intceil(T a, T b) { return (a + (b - 1)) / b; }
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;
typedef tuple<int,int,int> Tint;
typedef pair<ll,ll> PL;
const long long MOD = 1e9+7;
#define precout() cout << std::fixed << std::setprecision(20);
#define print(a) cout << a << endl;
template<typename T> void printv(vector<T>&v) {
    int n = v.size() - 1;
    rep(i, n) cout << v[i] << " ";
    cout << v.back() << endl;
}
const string alphabet = "abcdefghijklmnopqrstuvwxyz";
const int dy[4] = { 0, 1, 0, -1 };
const int dx[4] = { 1, 0, -1, 0 };
// if(nextH >= 0 && nextH < H && nextW >= 0 && nextW < W)
static const long double pi = acos(-1.0);
typedef complex<ld> cd;

struct UnionFind {
    vector<int> par;

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

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

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

    bool merge(int x, int y) {
        x = root(x); y = root(y);
        if (x == y) return false;

        if (par[x] > par[y]) swap(x, y);
        par[x] += par[y];
        par[y] = x;

        return true;
    }

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

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

    int N; cin >> N;
    vector<long long> x(N), y(N);
    for (int i = 0; i < N; ++i) cin >> x[i] >> y[i];
    // Kruskal 法で使用する枝
    using pint = pair<int,int>;
    using Edge = pair<long long, pint>;
    vector<Edge> edges;

    // x 軸方向にソートして隣接している部分のみ
    vector<int> ids(N);
    iota(ids.begin(), ids.end(), 0);
    sort(ids.begin(), ids.end(), [&](int i, int j) { return x[i] < x[j]; });
    for (int i = 0; i+1 < ids.size(); ++i) {
        int u = ids[i], v = ids[i+1];
        edges.push_back(Edge(x[v] - x[u], pint(u, v)));
    }

    // y 軸方向にソートして隣接している部分のみ
    sort(ids.begin(), ids.end(), [&](int i, int j) { return y[i] < y[j]; });
    for (int i = 0; i+1 < ids.size(); ++i) {
        int u = ids[i], v = ids[i+1];
        edges.push_back(Edge(y[v] - y[u], pint(u, v)));
    }

    // Kruskal 法
    sort(edges.begin(), edges.end());
    UnionFind uf(N);
    long long res = 0;
    for (auto e : edges) {
        int u = e.second.first, v = e.second.second;
        long long cost = e.first;
        if (uf.same(u, v)) continue;
        uf.merge(u, v);
        res += cost;
    }
    cout << res << endl;
}


Measured memory_bytes: 9364