#include <bits/stdc++.h>
#define SIZE 300005
#define MOD 1000000007LL
#define EPS 1e-10
#define INF 2147483647
#define LLINF 9223372036854775807
#define REP(i,n) for(int i=0;i<n;i++)
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define DOWN(i,b,a) for(int i=b;i>=a;i--)
#define SET(a,c) memset(a,c,sizeof a)
#define BIT(i,j) ((i)>>(j))&1
#define ALL(o) (o).begin(), (o).end()
#define ERASE(o) (o).erase(unique((o).begin(),(o).end()), (o).end())
#define SQ(x) ((x)*(x))
using namespace std;
typedef long long ll;
typedef pair<ll,ll> Pll;
typedef pair<int, int> Pii;
typedef pair<double, double> Pdd;
typedef complex<double> dcomplex;
template<typename T> inline void priv(vector<T>a){REP(i,a.size()){cerr<<a[i]<<((i==a.size()-1)?"\n":" ");}}
ll gcd(ll a,ll b){int c=max(a,b);int d=min(a,b);return c==0||d==0?c:gcd(c%d,d);}
ll lcm(ll a,ll b){return a==0||b==0?0:a*b/gcd(a,b);}
ll modfact(ll a){ll b=1;FOR(i,2,a)b=b*i%MOD;return b;}
ll modpow(ll a, ll n){ll b=1;while (n>0){if(n&1)b=b*a%MOD;a=a*a%MOD;n>>=1;}return b;}
ll modcomb(ll n, ll k){ll b=1;k=min(n-k,k);DOWN(i,n,n-k+1)b=b*i%MOD;return b*modpow(modfact(k),MOD-2)%MOD;}

template<typename T> 
struct Edge {
    int src, dst; T w;
    Edge() {};
    Edge(int src, int dst, T w): src(src), dst(dst), w(w){}
    bool operator<(const Edge &e)const{return w != e.w ? w > e.w : (src != e.src ? src < e.src : dst < e.dst);}
    bool operator==(const Edge &e){return src == e.src && dst == e.dst;}
};

template<typename T> 
class Graph : public vector<vector<Edge<T>>> {
private:
    pair<T,int> _farthest(int p, int v) {
        pair<T,int> r(0,v);
        for(auto e : (*this)[v]) if(e.dst != p) {
            auto t = farthest(v,e.dst);
            t.first += e.w;
            if(t.first > r.first) r=t;
        }
        return r;
    }
    void _backward(
            Graph &h, int v, int s, int r,
            vector<int> &no, vector<vector<int>> &cmp,
            vector<int> &prev, vector<vector<int>> &next, vector<T> &mcost,
            vector<int> &mark, T &cost, bool &found) {
        const int n = h.size();
        if(mark[v]) {
            vector<int> tmp = no;
            found = true;
            do {
                cost += mcost[v];
                v = prev[v];
                if (v != s){
                    while (cmp[v].size() > 0) {
                        no[cmp[v].back()] = s;
                        cmp[s].push_back(cmp[v].back());
                        cmp[v].pop_back();
                    }
                }
            } while (v != s);
            for(auto j : cmp[s]) if(j!=r) for(int l=0;l<h[j].size();l++)
                if(no[h[j][l].src]!=s) h[j][l].w -= mcost[tmp[j]];
        }
        mark[v] = true;
        for(auto i : next[v]) if(no[i]!=no[v]&&prev[no[i]]==v)
            if (!mark[no[i]]||i==s)
                _backward(h,i,s,r,no,cmp,prev,next,mcost,mark,cost,found);
    }
    void _subaps(
            int current, int prev, int &timer,
            vector<bool> &visited, vector<int> &prenum,
            vector<int> &parent, vector<int> &lowest) {
        prenum[current]=lowest[current]=timer++;
        visited[current]=true;
        for(auto e : (*this)[current]) {
            int next = e.dst;
            if(!visited[next]) {
                parent[next]=current;
                _subaps(next,current,timer,visited,prenum,parent,lowest);
                lowest[current]=min(lowest[current],lowest[next]);
            } else if(next != prev) lowest[current]=min(lowest[current],prenum[next]);
        }
    }
    void _subbrs(
            int current, int prev, int &timer,
            vector<int>&prenum, vector<int>&lowest, set<Edge<T>>&bridges) {
        prenum[current]=lowest[current]=timer++;
        for(auto e : (*this)[current]) if(e.dst!=prev) {
            if(prenum[e.dst]==-1) {
                _subbrs(e.dst,current,timer,prenum,lowest,bridges);
                lowest[current]=min(lowest[current],lowest[e.dst]);
                if(prenum[current] < lowest[e.dst])
                    bridges.insert(Edge<T>(min(e.dst,e.src),max(e.dst,e.src)));
            }
            lowest[current]=min(lowest[current],prenum[e.dst]);
        }
    }

public:
    T inf;
    Graph(int n, T inf=numeric_limits<T>::max()){(*this).resize(n);}
    void direct(int s, int t, T w){(*this)[s].push_back(Edge<T>(s,t,w));}
    void undirect(int s, int t, T w){direct(s,t,w);direct(t,s,w);}
    /* 
    cost : O(|V|)
    */
    T diameter(void) {
        auto r = _farthest(-1, 0);
        auto t = _farthest(-1, r.second);
        return t.first;
    }

    /*
    s : start point
    cost : O(|E|+|V|log(|V|))
    dist : distances
    */
    vector<T> dijkstra(int s = 0) {
        const int n = (*this).size();
        priority_queue<Edge<T>> PQ;
        vector<T> dist(n,inf);
        dist[s] = 0; Edge<T> e(-1,s,0);
        PQ.push(e);
        while(!PQ.empty()) {
            auto f = PQ.top(); PQ.pop();
            int u = f.dst;
            if(dist[u] < f.w * (-1)) continue;
            for(int j=0;j<(*this)[u].size();j++) {
                int v = (*this)[u][j].dst;
                if(dist[v] > dist[u] + (*this)[u][j].w) {
                    dist[v] = dist[u] + (*this)[u][j].w;
                    Edge<T> e(-1,v,dist[v]*(-1));
                    PQ.push(e);
                }
            }
        }
        return dist;
    }

    /*
    s : start point
    cost : O(|V||E|)
    first : is negative cycle ?
    second : distances
    */
    pair<bool,vector<T>> bellman_ford(int s = 0){
        const int n = (*this).size();
        vector<T> dist(n,inf);
        dist[s] = 0;
        for(int i=0;i<n;i++) {
            bool update = false;
            for(int v=0;v<n;v++) for(auto e : (*this)[v]) {
                if (dist[v] != inf && dist[e.dst] > dist[v] + e.w) {
                    dist[e.dst] = dist[v] + e.w;
                    update = true;
                    if(i==n-1) return make_pair(true,dist);
                }
            }
            if(!update) break;
        }
        return make_pair(false,dist);
    }

    /*
    Minimum Spanning Tree (Prim's algorithm)
    r : root
    cost : O(|E|+|V|log|V|) (because priority_queue use pairing sort)
    first : total cost
    second : edges
    */
    pair<T, vector<Edge<T>>> MST(int r = 0)
    {
        const int n = (*this).size();
        vector<Edge<T>> U;
        T total = 0;
        vector<bool> visited(n,false);
        priority_queue<Edge<T>> Q;
        Q.push(Edge<T>(-1,r,0));
        while (!Q.empty())
        {
            auto e = Q.top(); Q.pop();
            if (visited[e.dst]) continue;
            U.push_back(e);
            total += e.w;
            visited[e.dst] = true;
            for(auto f : (*this)[e.dst]) if (!visited[f.dst]) Q.push(f);
        }
        return make_pair(total, U);
    }

    /*
    Minimum Spanning Arborescence(Chu-Liu/Edmond)
    r : root
    cost : O(|V||E|)
    */
    T MSA(int r = 0) {
        const int n = (*this).size();
        Graph<T> h(n);
        for(int i=0;i<n;i++) for(auto e : (*this)[i]) h[e.dst].push_back(e);
        vector<int> no(n);
        vector< vector<int> > cmp(n);
        for(int i=0;i<n;i++) cmp[i].push_back(no[i]=i);
        for (T cost=0;;) {
            vector<int> prev(n,-1);
            vector<T> mcost(n,inf);
            for(int j=0;j<n;j++) if(j!=r) for(auto e : h[j])
                if (no[e.src] != no[j])
                    if (e.w < mcost[no[j]])
                        mcost[no[j]] = e.w, prev[no[j]] = no[e.src];
            vector<vector<int>> next(n);
            for(int i=0;i<n;i++) if(prev[i]>=0)
                next[prev[i]].push_back(i);
            bool stop = true;
            vector<int> mark(n);
            for(int i=0;i<n;i++) if(i!=r&&!mark[i]&&!cmp[i].empty()) {
                bool found = false;
                _backward(h, i, i, r, no, cmp, prev, next, mcost, mark, cost, found);
                if (found) stop = false;
            }
            if (stop) {
                for(int i=0;i<n;i++) if(prev[i] >= 0) cost+=mcost[i];
                return cost;
            }
        }
    }

    /*
    articulation points
    costs O(|E|log|V|)
    */
    set<int> APs(void) {
        const int n = (*this).size();
        set<int> ap;
        if(n==1) return ap;
        int timer = 1;
        vector<bool> visited(n,false);
        vector<int> prenum(n), parent(n), lowest(n);
        _subaps(0,-1,timer,visited,prenum,parent,lowest);
        int np = 0;
        for(int i=1; i<n; i++) {
            int p = parent[i];
            if(p==0) np++;
            else if(prenum[p]<=lowest[i]) ap.insert(p);
        }
        if(np > 1) ap.insert(0);
        return ap;
    }

    /*
    bridges
    only undirect graph
    */
    set<Edge<T>> bridges(void) {
        const int n = (*this).size();
        set<Edge<T>> bridges;
        vector<int> prenum(n,-1), lowest(n,inf);
        int timer = 0;
        for(int i=0;i<n;i++) if(prenum[i]==-1)
            _subbrs(i,-1,timer,prenum,lowest,bridges);
        return bridges;
    }
};

int main() {
    ll N;
    cin >> N;
    vector<pair<ll, ll>> X(N), Y(N);
    ll x, y;
    REP(i, N) {
        cin >> x >> y;
        X[i] = make_pair(i, x);
        Y[i] = make_pair(i, y);
    }
    Graph<ll> G(N);
    sort(ALL(X), [](auto const& lhs, auto const& rhs) {
        return lhs.second < rhs.second;});
    sort(ALL(Y), [](auto const& lhs, auto const& rhs) {
        return lhs.second < rhs.second;});
    REP(i, N-1) {
        G.undirect(X[i].first, X[i+1].first, abs(X[i+1].second - X[i].second));
        G.undirect(Y[i].first, Y[i+1].first, abs(Y[i+1].second - Y[i].second));
    }
    auto ans = G.MST();
    cout << ans.first << endl;
	return 0;
}

Measured memory_bytes: 19172