#include <bits/stdc++.h>
using namespace std;
using LL = long long;
using LD = long double;
using PII = pair<int, int>;
using PLI = pair<long long, int>;
using PLL = pair<long long, long long>;
using TI = tuple<int, int, int>;
mt19937 mrand(random_device{}());
int rnd(int x) { return mrand() % x; }
template<class A, class B> ostream& operator <<(ostream& out, const pair<A, B> &p) {
    return out << "(" << p.first << ", " << p.second << ")";
}
template <typename T, size_t N>
ostream& operator <<(ostream& out, const array<T, N>& a) {
    out << "["; bool first = true;
    for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
    return out;
}
template <typename T>
ostream& operator <<(ostream& out, const vector<T>& a) {
    out << "["; bool first = true;
    for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
    return out;
}
template <typename T>
ostream& operator <<(ostream& out, const deque<T>& a) {
    out << "["; bool first = true;
    for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
    return out;
}
template <typename T, class Cmp>
ostream& operator <<(ostream& out, const set<T, Cmp>& a) {
    out << "{"; bool first = true;
    for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "}";
    return out;
}
template <typename T>
ostream& operator <<(ostream& out, const unordered_set<T>& a) {
    out << "{"; bool first = true;
    for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "}";
    return out;
}
template <typename U, typename T, class Cmp>
ostream& operator <<(ostream& out, const map<U, T, Cmp>& a) {
    out << "{"; bool first = true;
    for (auto& p : a) { out << (first ? "" : ", "); out << p.first << ":" << p.second; first = 0;} out << "}";
    return out;
}
template<class T> inline void YES(T condition) { 
    if(condition) cout << "YES" << '\n';
    else cout << "NO" << '\n';
}
template<class T> inline void Yes(T condition) {
    if(condition) cout << "Yes" << '\n';
    else cout << "No" << '\n';
}
template<class T> T gcd(T a, T b) {
    while (b) {
        T tmp = b;
        b = a % b;
        a = tmp;
    }
    return a;
}
template<class T> T lcm(T a, T b){
    return a / gcd(a, b) * b;
}

#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
    cerr << name << ": " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
    const char* comma = strchr(names + 1, ',');
    cerr.write(names, comma - names) << ": " << arg1 << " |";
    __f(comma + 1, args...);
}

long long qpow(long long a, long long b, int MOD) {
    if (b == 0) return 1;
    long long res = 1;
    while (b) {
        if (b & 1) res = (res * a) % MOD;
        a = (a * a) % MOD;
        b >>= 1;
    }
    return res;
}

const int MOD = 1e9 + 7;
const int maxn = 2e6;
int fac[maxn + 5];
int invfac[maxn + 5];
void init() {
    fac[0] = 1;
    for (int i = 1; i <= maxn; i++) fac[i] = 1LL * fac[i - 1] * i % MOD;
    invfac[maxn] = (int)(qpow(fac[maxn], MOD - 2, MOD));
    for (int i = maxn - 1; i >= 0; i--) invfac[i] = 1LL * invfac[i + 1] * (i + 1) % MOD;
}
int C(int n, int k) {
    assert(0 <= k && n >= k);
    int tmp = (int)(1LL * invfac[k] * invfac[n - k] % MOD);
    return (int)(1LL * fac[n] * tmp % MOD);
}

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

    int n;
    cin >> n;
    vector<PII> x(n), y(n);
    for (int i = 0; i < n; i++) {
        int nx, ny;
        cin >> nx >> ny;
        x[i] = {nx, i};
        y[i] = {ny, i};
    }
    sort(x.begin(), x.end());
    sort(y.begin(), y.end());
    vector<TI> ALL;
    for (int i = 0; i < n - 1; i++) {
        ALL.emplace_back(x[i + 1].first - x[i].first, x[i + 1].second, x[i].second);
        ALL.emplace_back(y[i + 1].first - y[i].first, y[i + 1].second, y[i].second);
    }
    sort(ALL.begin(), ALL.end());
    LL ans = 0;

    vector<int> fa(n);
    vector<int> sz(n, 1);
    iota(fa.begin(), fa.end(), 0);
    function<int(int)> Find = [&](int x) {
        return x == fa[x] ? x : fa[x] = Find(fa[x]);
    };
    function<bool(int, int)> Union = [&](int x, int y) {
        int px = Find(x), py = Find(y);
        if (px == py) return false;
        if (sz[px] > sz[py]) swap(px, py);
        fa[px] = py;
        sz[py] += sz[px];
        return true;
    };

    for (auto& t: ALL) {
        int cost = get<0>(t), u = get<1>(t), v = get<2>(t);
        if (!Union(u, v)) continue;
        ans += cost;
        if (sz[Find(u)] == n || sz[Find(v)] == n) break;
    }

    cout << ans << '\n';


    return 0;
}


Measured memory_bytes: 7960