#include <bits/stdc++.h>
using namespace std;

#define li long long int
#define rep(i, to) for (li i = 0; i < ((li)(to)); i++)
#define repp(i, start, to) for (li i = (li)(start); i < ((li)(to)); i++)
#define pb push_back
#define sz(v) ((li)(v).size())
#define bgn(v) ((v).begin())
#define eend(v) ((v).end())
#define allof(v) (v).begin(), (v).end()
#define dodp(v, n) memset(v, (li)n, sizeof(v))
#define bit(n) (1ll << (li)(n))
#define mp(a, b) make_pair(a, b)
#define rin rep(i, n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1

#define idp if (DBGP)
#define F first
#define S second
#define p2(a, b) idp cout << a << "\t" << b << endl
#define p3(a, b, c) idp cout << a << "\t" << b << "\t" << c << endl
#define p4(a, b, c, d) idp cout << a << "\t" << b << "\t" << c << "\t" << d << endl
#define p5(a, b, c, d, e) idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << endl
#define p6(a, b, c, d, e, f) idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t" << f << endl
#define p7(a, b, c, d, e, f, g) idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t" << f << "\t" << g << endl
#define p8(a, b, c, d, e, f, g, h) idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t" << f << "\t" << g << "\t" << h << endl
#define p9(a, b, c, d, e, f, g, h, i) idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t" << f << "\t" << g << "\t" << h << "\t" << i << endl
#define p10(a, b, c, d, e, f, g, h, i, j) idp cout << a << "\t" << b << "\t" << c << "\t" << d << "\t" << e << "\t" << f << "\t" << g << "\t" << h << "\t" << i << "\t" << j << endl
#define foreach(it, v) for (__typeof((v).begin()) it = (v).begin(); it != (v).end(); ++it)
#define p2p(x) idp p2((x).F, (x).S)
#define dump(x, n)                         \
    idp                                    \
    {                                      \
        rep(i, n) { cout << x[i] << " "; } \
        puts("");                          \
    }
#define dump2(x, n)                                                     \
    idp                                                                 \
    {                                                                   \
        rep(i, n) { cout << "[" << x[i].F << " , " << x[i].S << "] "; } \
        puts("");                                                       \
    }
#define dumpi(x)                  \
    idp                           \
    {                             \
        foreach (it, x)           \
        {                         \
            cout << (*it) << " "; \
        }                         \
        puts("");                 \
    }
#define dumpi2(x)                                               \
    idp                                                         \
    {                                                           \
        foreach (it, x)                                         \
        {                                                       \
            cout << "[" << (it)->F << " , " << (it)->S << "] "; \
        }                                                       \
        puts("");                                               \
    }

#define read2d(a, w, h) rep(i, h) rep(j, w) cin >> a[i][j]
#define dump2d(a, w, h)                   \
    rep(i, h)                             \
    {                                     \
        rep(j, w) cout << a[i][j] << " "; \
        puts("");                         \
    }

typedef pair<li, li> PI;

vector<pair<li, PI>> edges;

#define UF_NUM 100100

li parent[UF_NUM];

inline void init_uf() {
    rep(i, UF_NUM)parent[i] = i;
}

inline li find(li x) {
    if (parent[x] == x)return x;
    else return (parent[x] = find(parent[x]));
}

inline void union_(li x, li y) {
    li parent_x = find(x);
    li parent_y = find(y);
    parent[parent_x] = parent_y;
}

PI xs[100100];
PI ys[100100];
li xs_idx[100100];
li ys_idx[100100];
li n;

inline vector<PI> get_closest(li idx, PI* arr) {
    vector<PI> res;
    if (idx > 0) {
        res.pb(arr[idx - 1]);
    }
    if (idx < n - 1) {
        res.pb(arr[idx + 1]);
    }
    return res;
}

int main() {
    cin >> n;
    init_uf();
    rin{
        li x, y;
        cin >> x >> y;
        xs[i] = {x, i};
        ys[i] = {y, i};
    }
    sort(xs, xs + n);
    sort(ys, ys + n);
    rin{
        xs_idx[xs[i].S] = i;
        ys_idx[ys[i].S] = i;
    }

    rin{
        if (xs_idx[i] > 0) {
            li cost = xs[xs_idx[i]].F - xs[xs_idx[i] - 1].F;
            edges.emplace_back(cost, mp(xs[xs_idx[i]].S, xs[xs_idx[i] - 1].S));
        }
        if (xs_idx[i] < n - 1) {
            li cost = xs[xs_idx[i] + 1].F - xs[xs_idx[i]].F;
            edges.emplace_back(cost, mp(xs[xs_idx[i] + 1].S, xs[xs_idx[i]].S));
        }
        if (ys_idx[i] > 0) {
            li cost = ys[ys_idx[i]].F - ys[ys_idx[i] - 1].F;
            edges.emplace_back(cost, mp(ys[ys_idx[i]].S, ys[ys_idx[i] - 1].S));
        }
        if (ys_idx[i] < n - 1) {
            li cost = ys[ys_idx[i] + 1].F - ys[ys_idx[i]].F;
            edges.emplace_back(cost, mp(ys[ys_idx[i] + 1].S, ys[ys_idx[i]].S));
        }
    }

    // run kruscal
    sort(allof(edges));
    li res = 0;
    for (const auto& edge : edges) {
        li cost = edge.F;
        li from = edge.S.F;
        li to = edge.S.S;
        if (find(from) != find(to)) {
            union_(from, to);
            res += cost;
        }
    }
    cout << res << endl;

    return 0;
}

Measured memory_bytes: 20076