#include <vector>
#include <iostream>
#include <cmath>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <fstream>
#include <unistd.h>
#include <string.h>
#include <string>
#include <numeric>
#include <queue>
#include <deque>
#include <sstream>
#include <iomanip>
#include <set>
#include <stack>
#include <cassert>
#include <functional>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<char> vc;
typedef vector<vector<char>> vvc;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef pair<ll, ll> PL;
typedef vector<PL> vpl;
typedef vector<vector<PL>> vvpl;
const int INF = 1001001001;
const ll LINF = 1e17;
const double pi = 3.1415926535897932;
const string endstr = "\n";
#define FOR(i, a, b) for(ll i = (a); i < b; i++)
#define RFOR(i, a, b) for(ll i = (a); i > b; i--)
#define rep(i, n) for(ll i = 0; i < n; i++)
#define rrep(i, n) for(ll i = n-1; i > -1; i--)
#define FORMAP(it, m) for(auto it = m.begin(); it != m.end(); it++)
#define ff first
#define ss second
#define pb push_back
#define epb emplace_back
#define ALL(X) (X).begin(),(X).end()

template <typename T>
T gcd(T a, T b) {
    return (a == 0) ? b : gcd(b%a, a);
}
template <typename T>
T lcm(T a, T b) {
    return a / gcd(a, b) * b;
}

bool p_comp_fs(const PL p1, const PL p2){ return p1.first < p2.first;};
bool p_comp_fg(const PL p1, const PL p2){ return p1.first > p2.first;};
bool p_comp_ss(const PL p1, const PL p2){ return p1.second < p2.second;};
bool p_comp_sg(const PL p1, const PL p2){ return p1.second > p2.second;};
template <typename T>
vector<T> uniquen(vector<T> vec){
    sort(ALL(vec));
    vec.erase(unique(vec.begin(), vec.end()), vec.end());
    return vec;
}

inline ll popcnt(ll x){return __builtin_popcountll((unsigned long long)x);};
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
//friend bool operator<(const stc& lhs, const stc& rhs){
//    return std::tie(lhs.l, lhs.r) < std::tie(rhs.l, rhs.r);
//}

struct UnionFind{
    vl par;
    vl rank;
    map<ll, ll> size;
    UnionFind(ll N) : par(N, 0), rank(N, 0){
        for(ll i = 0; i < N; i++){
            par[i] = i; size[i] = 1;
        }
    }
    
    ll root(ll x){
        if(par[x] == x) return x;
        else{
            par[x] = root(par[x]); // compression
            return par[x];
        }
    }
    
    void unite(ll x, ll y){
        ll rx = root(x); ll ry = root(y);
        if(rx == ry) return;
        if(rank[rx] < rank[ry]) swap(rx, ry);
        if(rank[rx] == rank[ry]) ++rank[rx];
        par[ry] = rx;
        if(rx != ry) size[rx] = size[rx] + size[ry];
        else{
            size[rx] = max(size[rx], size[ry]);
        }
    }
    
    ll get_size(ll x){
        return size[root(x)];
    }
    
    bool same(ll x, ll y){
        return root(x) == root(y);
    }
};



struct edge {
    ll cost, from, to;
    friend bool operator<(const edge& lhs, const edge& rhs){
        return lhs.cost < rhs.cost;
    }
};

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    ll N; cin >> N;
    multimap<ll, ll> xs, ys;
    rep(i, N){
        ll x, y; cin >> x >> y;
        xs.emplace(x, i);
        ys.emplace(y, i);
    }
    
    vector<edge> edges;
    FORMAP(it, xs) if(next(it) != xs.end()){
        ll c = next(it)->ff - it->ff;
        edges.pb({c, it->ss, next(it)->ss});
    }
    FORMAP(it, ys) if(next(it) != ys.end()){
        ll c = next(it)->ff - it->ff;
        edges.pb({c, it->ss, next(it)->ss});
    }
    
    sort(ALL(edges));
    
    ll ans = 0;
    auto uf = UnionFind(N);
    rep(i, edges.size()){
        ll f = edges[i].from, t = edges[i].to;
        if(uf.same(f, t)) continue;
        ans += edges[i].cost;
        uf.unite(f, t);
    }
    cout << ans << endstr;
    return 0;
}


Measured memory_bytes: 26732