#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(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

typedef long long LL;
template<typename T> using V = std::vector<T>;
template<typename T> using VV = std::vector<std::vector<T>>;
template<typename T> using VVV = std::vector<std::vector<std::vector<T>>>;

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); }

const int INF = 1L << 30;
const double EPS = 1e-9;
const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy4 = { 0, 1, 0, -1 }, dx4 = { 1, 0, -1, 0 };    // 4近傍（右, 下, 左, 上）
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 from;
    int to;
    int cost;
    Edge(int from, int to, int cost) : 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(unsigned int num_of_node, vector<Edge> &edges) {
    sort(edges.begin(), edges.end());

    UnionFind uf(num_of_node);

    long long ans = 0;
    for (Edge 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);

	int N;
	cin >> N;
    vector<pair<int, int>> xs(N), ys(N);
    FOR(i, 0, N) {
        int x, y;
        cin >> x >> y;
        xs[i] = make_pair(x, i);
        ys[i] = make_pair(y, i);
    }

    sort(ALL(xs));
    sort(ALL(ys));

    vector<Edge> edges;
    FOR(i, 0, N - 1) {
        int dx = abs(xs[i].first - xs[i + 1].first);
        edges.emplace_back(Edge(xs[i].second, xs[i + 1].second, dx));
        edges.emplace_back(Edge(xs[i + 1].second, xs[i].second, dx));

        int dy = abs(ys[i].first - ys[i + 1].first);
        edges.emplace_back(Edge(ys[i].second, ys[i + 1].second, dy));
        edges.emplace_back(Edge(ys[i + 1].second, ys[i].second, dy));
    }

    print(kruskal(N, edges));

	return 0;
}

Measured memory_bytes: 9968