#include <iostream>
#include <map>
#include <vector>
#include <algorithm>
#include <string>
#include <queue>
#include <iomanip>
#include <set>
#include <unordered_map>

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

using namespace std;

#define rep(i,n) for(int i=0,i##_len=(n);i<i##_len;++i)
#define repx(i,s,d,e) for(int i=s,i##_end=(e);i<i##_end;i+=d)
#define rept(n) for(int ___i___=0,i##_len=(n);___i___<i##_len;++___i___)
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define ALL(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define ZERO(a) memset(a,0,sizeof(a))
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(v.begin(),v.end()),v.end());
#define CEIL(x, y) (((x) + (y) - 1) / (y))

// vector
template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec) is >> x;
    return is;
}
// pair
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}
// vector
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &vec) {
    os << "{";
    for (int i = 0; i < vec.size(); i++) {
        os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
    }
    os << "}";
    return os;
}
// map
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
    os << "{";
    repi(itr, map_var) {
        os << *itr;
        itr++;
        if (itr != map_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
// set
template <typename T>
ostream &operator<<(ostream &os, set<T> &set_var) {
    os << "{";
    repi(itr, set_var) {
        os << *itr;
        itr++;
        if (itr != set_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
#define DUMPOUT cout
void dump_func() {
    DUMPOUT << endl;
}
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) {
        DUMPOUT << ", ";
    }
    dump_func(std::move(tail)...);
}
#ifdef LOCAL_
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define dump(...)
#endif

typedef long long int lli;
typedef pair<int, int> ii;
typedef priority_queue<int, vector<int>, greater<int> > heapq;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
struct aaa{
    aaa(){
        cin.tie(0); ios::sync_with_stdio(0); cout<<fixed<<setprecision(20);
    };
}aaaaaaa;

class UnionFindWithSize {
    public:
        UnionFindWithSize(int N) : parent(N, -1) {}
        void unite(int x, int y) {
            x = find(x);
            y = find(y);
            if (x == y) return;
            if (parent[x] > parent[y]) swap(x, y);
            parent[x] += parent[y];
            parent[y] = x;
        }
        int find(int x) {
            if (parent[x] < 0) return x;
            return parent[x] = find(parent[x]);
        }
        int size(int x) {
            return -parent[find(x)];
        }
    private:
        vector<int> parent;
};

signed main() {
    int N; cin >> N;
    vector<ii> ix(N), iy(N);
    rep(i, N) {
        int _x, _y; cin >> _x >> _y;
        ix[i] = ii(i, _x); iy[i] = ii(i, _y);
    }

    auto cmp = [](auto const& lhs, auto const& rhs) {
        return lhs.second < rhs.second;
    };
    sort(ALL(ix), cmp);
    sort(ALL(iy), cmp);

    vector<pair<ii, int> > edges(2 * (N - 1));
    rep(i, N - 1) {
        int lv = ix[i].first, rv = ix[i + 1].first;
        int bv = iy[i].first, tv = iy[i + 1].first;
        edges[i] = pair<ii, int>(ii(lv, rv), ix[i + 1].second - ix[i].second);
        edges[i + N - 1] = pair<ii, int>(ii(bv, tv), iy[i + 1].second - iy[i].second);
    }
    sort(ALL(edges), cmp);

    lli ans = 0;
    UnionFindWithSize ufws(N);
    rep(i, 2 * (N - 1)) {
        ii uv = edges[i].first;
        int u = uv.first, v = uv.second;
        if (ufws.find(u) == ufws.find(v)) {
            continue;
        }
        int d = edges[i].second;
        ufws.unite(u, v);
        ans += d;
    }
    cout << ans << endl;
}


Measured memory_bytes: 4608