/**
 *    author:  zjsdut
 *    created: 2020/01/17 09:10:25
**/
#include <bits/stdc++.h>

using namespace std;

struct fast_ios {
    fast_ios() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(10);
    };
} fast_ios_;

template<typename A, typename B>
bool chkmin(A &a, const B &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}

template<typename A, typename B>
bool chkmax(A &a, const B &b) {
    if (b > a) {
        a = b;
        return true;
    }
    return false;
}

template<typename T>
istream &operator>>(istream &stream, vector<T> &vec) {
    for (auto &x : vec) stream >> x;
    return stream;
}

void scan() {}

template<class T, class ...Args>
void scan(T &a, Args &...rest) {
    cin >> a;
    scan(rest...);
}

using ll = long long;
using vl = vector<ll>;
using vb = vector<bool>;
using vi = vector<int>;
using pii = pair<int, int>;
template<typename T> using vv = vector<vector<T>>;
#define rng(i, a, b) for(int i = (int)(a); i < (int)(b); ++i)
#define up(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define down(i, b, a) for (int i = int(b); i >= int(a); i--)
#define rep(n) for(int _iter_##n = 0, _num_##n = (int)n; _iter_##n < _num_##n; ++_iter_##n)
#define FOR(x, cont) for (const auto &x: cont)
#define For(x, cont) for (auto &x: cont)
#define all(x) begin(x), end(x)
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define ep emplace
#define SZ(x) (int)(x).size()
#define UNIQ(vec) (vec).erase(unique(all(vec)), end(vec))
#define LB(cont, x) int(lower_bound(all(cont), x) - begin(cont))
#define UB(cont, x) int(upper_bound(all(cont), x) - begin(cont))

template<typename T>
ostream &operator<<(ostream &stream, const vector<T> &vec) {
    if (!vec.empty()) {
        stream << vec[0];
        for (size_t i = 1; i != vec.size(); ++i)
            stream << ' ' << vec[i];
    }
    return stream;
}

template<typename T>
void print(const vector<T> &t) { cout << t << '\n'; }

template<typename T>
void print(const vector<vector<T>> &t) {
    for (const auto &row : t) {
        print(row);
    }
}

template<typename T>
void print(const T &t) { cout << t << ' '; }

template<typename T, typename ...Args>
void print(const T &t, const Args &...rest) {
    print(t);
    print(rest...);
}

template<typename T>
void println(const T &t) { cout << t << '\n'; }

template<typename T, typename ...Args>
void println(const T &t, const Args &...rest) {
    print(t);
    println(rest...);
}

class UnionFind {
    vi par, sz;
    int nTree;
public:
    explicit UnionFind(int n) : par(n), sz(n, 1), nTree(n) { //0-indexed
        iota(par.begin(), par.end(), 0);
    }

    int n_tree() const {
        return nTree;
    }

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

    int root(int x) {
        return x == par[x] ? x : par[x] = root(par[x]);
    }

    bool unite(int x, int y) {
        int rx = root(x), ry = root(y);
        if (rx != ry) {
            par[rx] = ry;
            --nTree;
            sz[ry] += sz[rx];
            return true;
        }
        return false;
    }

    bool is_root(int x) const {
        return par[x] == x;
    }
};
int main() {
#if defined LOCAL
    ifstream in("in.txt");
    cin.rdbuf(in.rdbuf());
#endif
    int n;
    scan(n);
    vector<pii> p(n);
    For (x, p) {
        scan(x.first, x.second);
    }
    vi a(n);
    iota(all(a), 0);
    sort(all(a), [&](int x, int y){return p[x].first < p[y].first;});
    vector<array<int,3>> e;
    rng (i, 1, n) {
        int x = a[i], y = a[i - 1];
        e.pb({p[x].first - p[y].first, x, y});
    }
    sort(all(a), [&](int x, int y){return p[x].second < p[y].second;});
    rng (i, 1, n) {
        int x = a[i], y = a[i - 1];
        e.pb({p[x].second - p[y].second, x, y});
    }
    sort(all(e));
    UnionFind b(n);
    int ans = 0;
    FOR (x, e) {
        if (b.unite(x[1], x[2])) {
            ans += x[0];
        }
    }
    println(ans);
    return 0;
}

Measured memory_bytes: 6132