#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_ON(bit, i) (((bit >> i) & 1) > 0)

typedef long long LL;
template<typename T> std::vector<T> make_v(size_t a){return std::vector<T>(a);}
template<typename T,typename... Ts> auto make_v(size_t a, Ts... ts){ return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}    // C++14
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }

template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}
// 初項s, 交差dのn個の数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
    return n * (2 * s + (n - 1) * d) / 2;
}

// 2のべき乗数かどうか
bool is_power_of_two(long long x) {
    return !(x & (x - 1));
}

// aとbの最大公約数 O(log min(a, b))
long long gcd(long long a, long long b) {
    if (b == 0) { return a; }
    return gcd(b, a % b);
}

// 数列vの最大公約数 O(N log d)
long long gcd(std::vector<long long> &v) {
    long long ans = v[0];
    for (int i = 1; i < v.size(); ++i) {
        ans = gcd(ans, v[i]);
    }
    return ans;
}

// aとbの最小公倍数 O(log min(a, b))
long long lcm(long long a, long long b) {
    long long g = gcd(a, b);
    return a / g * b;
}

const int INF = 1 << 30;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy2 = {0, 1}, dx2 = {1, 0};  // 右，下
const std::vector<int> dy4 = {0, -1, 0, 1}, dx4 = {1, 0, -1, 0};    // 右，上，左，下
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };



using namespace std;

struct Edge {
    int no;
    int from;
    int to;
    long long cost;
    Edge() {}
    Edge(int from, int to, long long cost) : from(from), to(to), cost(cost) {}
    Edge(int no, int from, int to, long long cost) : no(no), from(from), to(to), cost(cost) {}
    bool operator<(const Edge& edge) const {
        return this->cost < edge.cost;
    }
    bool operator>(const Edge& edge) const {
        return this->cost > edge.cost;
    }
};

class UnionFind {
public:
    vector<int> parent;
    vector<int> setSize;

    UnionFind(unsigned int size) {
        parent.resize(size + 1);
        iota(parent.begin(), parent.end(), 0);
        setSize.resize(size + 1, 1);
    }

    // xとyが同じ集合に属するか
    bool isSameSet(int x, int y) {
        return findRoot(x) == findRoot(y);
    }

    // xとyの属する集合を併合
    void unionSet(int x, int y) {
        x = findRoot(x);
        y = findRoot(y);
        if (x == y) { return; }

        parent[x] = y;
        setSize[y] += setSize[x];
    }

private:
    // 木の根を求める
    int findRoot(int x) {
        if (parent[x] == x) {
            return x;
        }
        else {
            return parent[x] = findRoot(parent[x]);
        }
    }
};

/**
 * グラフの最小全域木を求める。O(|E| log|V|)
 * @param num_of_node ノード数
 * @param edges　エッジ　無向グラフならu -> vとv -> uの両方向入れる
 * @return
 */
long long kruskal(int num_of_node, vector<Edge> &edges) {
    sort(edges.begin(), edges.end());

    UnionFind uf(num_of_node);
    long long ans = 0;
    for (const auto e : edges) {
        if (!uf.isSameSet(e.from, e.to)) {
            uf.unionSet(e.from, e.to);
            ans += e.cost;
        }
    }

    return ans;
}

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

    LL N;
    cin >> N;

    vector<pair<int, int>> xs, ys;
    FOR(i, 0, N) {
        int X, Y;
        cin >> X >> Y;

        xs.emplace_back(make_pair(X, i));
        ys.emplace_back(make_pair(Y, i));
    }
    sort(ALL(xs));
    sort(ALL(ys));

    vector<Edge> edges;
    FOR(i, 0, N - 1) {
        int x1 = xs[i].first;
        int c1 = xs[i].second;
        int x2 = xs[i + 1].first;
        int c2 = xs[i + 1].second;
        edges.emplace_back(Edge(c1, c2, abs(x1 - x2)));
        edges.emplace_back(Edge(c2, c1, abs(x1 - x2)));
    }
    FOR(i, 0, N - 1) {
        int y1 = ys[i].first;
        int c1 = ys[i].second;
        int y2 = ys[i + 1].first;
        int c2 = ys[i + 1].second;
        edges.emplace_back(Edge(c1, c2, abs(y1 - y2)));
        edges.emplace_back(Edge(c2, c1, abs(y1 - y2)));
    }

    print(kruskal(N, edges));

    return 0;
}


Measured memory_bytes: 16864