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

#define rep(i,n) for(long long i = 0; i < (long long)(n); i++)
#define repi(i,a,b) for(long long i = (long long)(a); i < (long long)(b); i++)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define mt make_tuple
#define mp make_pair
template<class T1, class T2> bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); }
template<class T1, class T2> bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

using ll = long long; using vll = vector<ll>; using vvll = vector<vll>; using P = pair<ll, ll>;
using ld = long double;  using vld = vector<ld>; 
using vi = vector<int>; using vvi = vector<vi>; vll conv(vi& v) { vll r(v.size()); rep(i, v.size()) r[i] = v[i]; return r; }

inline void input(int &v){ v=0;char c=0;int p=1; while(c<'0' || c>'9'){if(c=='-')p=-1;c=getchar();} while(c>='0' && c<='9'){v=(v<<3)+(v<<1)+c-'0';c=getchar();} v*=p; }
template <typename T, typename U> ostream &operator<<(ostream &o, const pair<T, U> &v) {  o << "(" << v.first << ", " << v.second << ")"; return o; }
template<size_t...> struct seq{}; template<size_t N, size_t... Is> struct gen_seq : gen_seq<N-1, N-1, Is...>{}; template<size_t... Is> struct gen_seq<0, Is...> : seq<Is...>{};
template<class Ch, class Tr, class Tuple, size_t... Is>
void print_tuple(basic_ostream<Ch,Tr>& os, Tuple const& t, seq<Is...>){ using s = int[]; (void)s{0, (void(os << (Is == 0? "" : ", ") << get<Is>(t)), 0)...}; }
template<class Ch, class Tr, class... Args> 
auto operator<<(basic_ostream<Ch, Tr>& os, tuple<Args...> const& t) -> basic_ostream<Ch, Tr>& { os << "("; print_tuple(os, t, gen_seq<sizeof...(Args)>()); return os << ")"; }
ostream &operator<<(ostream &o, const vvll &v) { rep(i, v.size()) { rep(j, v[i].size()) o << v[i][j] << " "; o << endl; } return o; }
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T> ostream &operator<<(ostream &o, const deque<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const unordered_set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U>  ostream &operator<<(ostream &o, const map<T, U> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U, typename V>  ostream &operator<<(ostream &o, const unordered_map<T, U, V> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it; o << "]";  return o; }
vector<int> range(const int x, const int y) { vector<int> v(y - x + 1); iota(v.begin(), v.end(), x); return v; }
template <typename T> istream& operator>>(istream& i, vector<T>& o) { rep(j, o.size()) i >> o[j]; return i;}
template <typename T, typename S, typename U> ostream &operator<<(ostream &o, const priority_queue<T, S, U> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.top(); tmp.pop(); o << x << " ";} return o; }
template <typename T> ostream &operator<<(ostream &o, const queue<T> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.front(); tmp.pop(); o << x << " ";} return o; }
template <typename T> ostream &operator<<(ostream &o, const stack<T> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.top(); tmp.pop(); o << x << " ";} return o; }
template <typename T> unordered_map<T, ll> counter(vector<T> vec){unordered_map<T, ll> ret; for (auto&& x : vec) ret[x]++; return ret;};
string substr(string s, P x) {return s.substr(x.fi, x.se - x.fi); }
void vizGraph(vvll& g, int mode = 0, string filename = "out.png") { ofstream ofs("./out.dot"); ofs << "digraph graph_name {" << endl; set<P> memo; rep(i, g.size())  rep(j, g[i].size()) { if (mode && (memo.count(P(i, g[i][j])) || memo.count(P(g[i][j], i)))) continue; memo.insert(P(i, g[i][j])); ofs << "    " << i << " -> " << g[i][j] << (mode ? " [arrowhead = none]" : "")<< endl;  } ofs << "}" << endl; ofs.close(); system(((string)"dot -T png out.dot >" + filename).c_str()); }
size_t random_seed; namespace std { using argument_type = P; template<> struct hash<argument_type> { size_t operator()(argument_type const& x) const { size_t seed = random_seed; seed ^= hash<ll>{}(x.fi); seed ^= (hash<ll>{}(x.se) << 1); return seed; } }; }; // hash for various class
struct timeval start; double sec() { struct timeval tv; gettimeofday(&tv, NULL); return (tv.tv_sec - start.tv_sec) + (tv.tv_usec - start.tv_usec) * 1e-6; }
struct init_{init_(){ ios::sync_with_stdio(false); cin.tie(0); gettimeofday(&start, NULL); struct timeval myTime; struct tm *time_st; gettimeofday(&myTime, NULL); time_st = localtime(&myTime.tv_sec); srand(myTime.tv_usec); random_seed = RAND_MAX / 2 + rand() / 2; }} init__;
#define ldout fixed << setprecision(40) 

#define EPS (double)1e-14
#define mo  (ll)(1e9+7)

/***********************/
// 共通部分
/***********************/
#define REP(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()

typedef long long Weight;
const Weight INF = 1e18;

struct Edge {
    ll src, dst;
    Weight weight; // 最小費用流ではcostの役割
    ll cap;
    ll rev; // 残余グラフの対応用
    bool rev_flag = false; // revなら1
    Edge(int src = 0, int dst = 0, int weight = 0, Weight cap = 1): 
        src(src), dst(dst), weight(weight), cap(cap){ }
};
bool operator < (const Edge &e, const Edge &f) {
    return e.weight != f.weight ? e.weight > f.weight : // !!INVERSE!!
        e.src != f.src ? e.src < f.src : e.dst < f.dst;
}
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

typedef vector<Weight> Array;
typedef vector<Array> Matrix;

// 最大流と最小費用流の有向
// 無向は自分でひっくり返して追加して下さい
void addDirected(Graph& g, ll src, ll dst, Weight weight = 0, ll cap = 0) {
    assert(src < g.size() && src >= 0 && dst < g.size() && dst >= 0);
    g[src].push_back(Edge(src, dst, weight, cap)); 
}
vector<string> names;
unordered_map<string, int> name_server;
void clearNameServer(void) {
    names.clear();
    name_server.clear();
}
int constructNameServer(vector<string>& names_) {
    names = names_;
    for (int i = 0; i < names.size(); i++) {
        name_server[names[i]] = i;
    }
    return name_server.size();
}
void addDirected(Graph& g, string src, string dst, Weight weight = 0, ll cap = 0) {
    if (!name_server.count(src)) { cerr << "No such node : " << src << endl; exit(1); }
    if (!name_server.count(dst)) { cerr << "No such node : " << dst << endl; exit(1); }
    addDirected(g, name_server[src], name_server[dst], weight, cap);
}

void addUndirected(Graph& g, ll src, ll dst, Weight weight = 0, ll cap = 0) { 
    addDirected(g, src, dst, weight, cap);
    addDirected(g, dst, src, weight, cap);
} 

void transformFromMatrixToGraph(Graph& g, Matrix& m) {
    ll n = m.size();
    g.resize(n);
    rep(i, n) rep(j, n) if (m[i][j] != INF) {
        addDirected(g, i, j, m[i][j]);
    }
}

void printGraph(Graph& g) {
    rep(i, g.size()) {
        if (!g[i].size())
            continue;
        rep(j, g[i].size()) 
            cout << "(" << i << ", " << g[i][j].dst << "), ";
        cout << endl;
    }
}
void printGraphCap(Graph& g) {
    rep(i, g.size()) {
        if (!g[i].size())
            continue;
        rep(j, g[i].size()) 
            cout << "(" << i << ", " << g[i][j].dst << " : " << g[i][j].cap << ", " << (g[i][j].rev_flag ? "rev" : "for") << "), ";
        cout << endl;
    }
}

// mode
//
// 0 : デフォルト。辺だけ表示
// 1 : 重みweightだけ表示
// 2 : フロー用。weight, capを表示。
void vizGraph(Graph& g, int mode = 0, string filename = "out.png") {
    ofstream ofs("./out.dot");
    ofs << "digraph graph_name {" << endl;
    rep(i, g.size()) {
        if (!g[i].size())
            continue;
        rep(j, g[i].size()) {
            if (name_server.size()) {
                ofs << "    " << names[i] << " -> " << names[g[i][j].dst]; 
            } else {
                ofs << "    " << i << " -> " << g[i][j].dst; 
            }
            if (mode == 1) {
                ofs << " [ label = \"" << g[i][j].weight << "\"];"; 
            } else if (mode == 2) {
                ofs << " [ label = \"" << g[i][j].weight << "/" << (g[i][j].cap  == INF ? "inf" : to_string(g[i][j].cap)) << "\"];"; 
            }
            ofs << endl;
        }
    }
    ofs << "}" << endl;
    ofs.close();
    system(((string)"dot -T png out.dot >" + filename).c_str());
}



/***********************/
// 共通部分おわり
/***********************/

// Prim
// O(E log V)
pair<Weight, Edges> minimumSpanningTree(const Graph &g, ll r = 0) {
    ll n = g.size();
    Edges T;
    Weight total = 0;

    vector<bool> visited(n);
    priority_queue<Edge> Q;
    Q.push( Edge(-1, r, 0) );
    while (!Q.empty()) {
        Edge e = Q.top(); Q.pop();
        if (visited[e.dst]) continue;
        T.push_back(e);
        total += e.weight;
        visited[e.dst] = true;
        FOR(f, g[e.dst]) if (!visited[f->dst]) Q.push(*f);
    }
    return pair<Weight, Edges>(total, T);
}


//void addUndirected(Graph& g, ll src, ll dst, Weight weight = 0, ll cap = 0) { 

int main(void) {
    ll n; cin >> n;
    vector<vll> p; 
    Graph g(n);
    rep(i, n) {
        ll x,y;cin>>x>>y;
        p.pb({x,y,i});
    }

    map<P, ll> memo;
    rep(_, 2) {
        sort(all(p));
        rep(i, n-1) {
            ll d = p[i+1][0]-p[i][0];
            if (memo.count(P(p[i][2], p[i+1][2]))) {
                chmin(memo[P(p[i][2], p[i+1][2])], d);
                chmin(memo[P(p[i+1][2], p[i][2])], d);
            } else {
                memo[P(p[i][2], p[i+1][2])] = d;
                memo[P(p[i+1][2], p[i][2])] = d;
            }
        }

        rep(i, n) swap(p[i][0],p[i][1]);
    }


    for (auto x : memo) 
        addDirected(g, x.fi.fi, x.fi.se, x.se);

//    printGraph(g);

//    vizGraph(g, 1);
    auto x = minimumSpanningTree(g);
    cout << x.fi << endl;

    return 0;
}


Measured memory_bytes: 70184