#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define countof(array) (sizeof(array) / sizeof(array[0]))
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,n,s) for(int i = s; i < (n); ++i)
#define rsrep(i,n,s) for(int i = (n)-1; i >= s; --i)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define aall(a) (a), (a)+countof(a)//for array sorting
#define raall(a) (a), (a)+countof(a), greater<>()
#define show(x) cout<<#x<<" = "<<x<<endl;
#define vfind(v, a) find(all(v), a) != v.end()
#define yn(f) { if (f) puts("YES"); else puts("NO"); }
#define yns(f) { if (f) puts("Yes"); else puts("No"); }
#define show_ary(...) { cout<<#__VA_ARGS__<<" = "; for (const auto& x : (__VA_ARGS__)) { cout<<x<<" "; } cout<<endl; }
#define show_pair(...) cout<<#__VA_ARGS__<<" = "<<endl; for (const auto& x : (__VA_ARGS__)) { cout<<"  "<<x.fi<<" : "<<x.se<<endl; }
#define out_ary(...) { for (const auto& x : (__VA_ARGS__)) { cout<<x<<" "; } cout<<endl; }
#define argmax(v) distance((v).begin(), max_element(all(v)))
#define argmin(v) distance((v).begin(), min_element(all(v)))
#define vmax(v) *max_element(all(v))
#define vmin(v) *min_element(all(v))
typedef long long int ll;
typedef pair<int, int> P;
typedef vector<P> vpair;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef vector<double> vdouble;
typedef vector<string> vstr;
typedef vector<bool> vbool;
typedef vector<vint> vvint;
typedef vector<vll> vvll;
typedef vector<vstr> vvstr;
typedef vector<vbool> vvbool;
const ll LINF = 2000000000000000000ll;
const int INF = 1000000100;
const ll MOD = 1e9+7;

struct UnionFind {
    vector<int> par, rank;

    UnionFind(int n) {
        par.resize(n), rank.resize(n, 0);
        for(int i = 0; i < n; i++) par[i] = i; 
    }

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

    bool same(int x, int y) {
        return root(x) == root(y);
    }

    void unite(int x, int y) {
        x = root(x);
        y = root(y);
        if (x == y) return;
        if (rank[x] < rank[y]) par[x] = y;
        else {
            par[y] = x;
            if (rank[x] == rank[y]) rank[x]++;
        }
    }
};

int main() {
    int n;
    cin >> n;

    vpair px(n), py(n);
    rep(i, n) {
        px[i].se = i;
        py[i].se = i;
        cin >> px[i].fi >> py[i].fi;
    }
    sort(all(px));
    sort(all(py));

    vector<tuple<int, int, int>> edges;//cost, from, to
    rep(i, n-1) {
        edges.emplace_back(px[i+1].fi - px[i].fi, px[i].se, px[i+1].se);
        edges.emplace_back(py[i+1].fi - py[i].fi, py[i].se, py[i+1].se);
    }
    sort(all(edges));

    /*
    show_pair(px);
    show_pair(py);
    for (auto edge : edges) {
        int d, from, to;
        tie(d, from, to) = edge;
        cout << d << " " << from << " " << to << endl;
    }
    cout << endl;
    //*/

    int ans = 0;
    UnionFind uf(n);
    for (auto edge : edges) {
        int d, from, to;
        tie(d, from, to) = edge;
        if (uf.same(from, to) == false) {
            //cout << d << " " << from << " " << to << endl;
            ans += d;
            uf.unite(from, to);
        }
    }

    cout << ans << endl;
    return 0;
}

Measured memory_bytes: 6388