#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdarg>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>

#define whlie while
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define inf 1001001001
#define infLL ( (1LL << 61) - 10)
#define mod 1000000007
#define FOR(i,a,b) for(int (i)=((int)a); (i)<((int)b); (i)++) // [a,b)
#define rep(i,N) FOR((i), 0, ((int)N)) // [0,N)
#define FORR(i,a,b) for(int (i)=((int)b) - 1; (i)>=((int)a); (i)--)
#define repr(i,N) FORR((i), 0, ((int)N))
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
#define vrep(v,it) for(auto it=v.begin();it<v.end();it++)
#define vrepr(v,it) for(auto it=v.rbegin();it<v.rend();it++)
#define inx(t,...) t __VA_ARGS__; in(__VA_ARGS__)
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) ll __VA_ARGS__; in(__VA_ARGS__)
#define inc(...) char __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
#define ind(...) double __VA_ARGS__; in(__VA_ARGS__)
#define inpii(...) pii __VA_ARGS__; in(__VA_ARGS__)
#define invi(v,...) vi v; in(v,##__VA_ARGS__)
#define invl(v,...) vl v; in(v,##__VA_ARGS__)
#define mem(ar,val) memset((ar), (val), sizeof(ar) )

#ifdef LOCAL
    #define dbg(...) fprintf(stderr, __VA_ARGS__)
    #define trc(...) do { cout << #__VA_ARGS__ << "="; dbg_out(__VA_ARGS__);} while(0)
    #define stopif(val) assert( !(val) )
    #define vdbg(v,...) do { cout << #v << " = "; vector_debug(v , ##__VA_ARGS__);} while(0)
#else
    #define dbg(...) 1
    #define trc(...) 1
    #define stopif(...) 1
    #define vdbg(...) 1
#endif

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<string> vs;
typedef vector<pii> vpii;
typedef vector< vector<int> > vvi;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

int gcd(int a, int b){if(a>b) swap(a,b); return a==0 ? b : gcd(b%a,a);} ll gcd(ll a, ll b){if(a>b) swap(a,b); return a==0 ? b : gcd(b%a,a);}
int lcm(int a, int b){return (a / gcd(a,b)) * b;} ll lcm(ll a, ll b){return (a / gcd(a,b)) * b;}
inline int pow(int a, int b){int ans = 1; rep(i,b) ans *= a; return ans;} inline ll pow(ll a, ll b){ll ans = 1; rep(i,b) ans*= a; return ans;}
inline ll pow(int a, ll b){ll ans = 1; rep(i,b) ans*= a; return ans;} inline ll pow(ll a, int b){ll ans = 1; rep(i,b) ans*= a; return ans;}
template<typename T, typename U> inline bool amin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template<typename T, typename U> inline bool amax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
template<typename C> inline void _cin(C &c){cin >> c;}
template<typename T,typename U> inline void _cin(pair<T,U> &p){cin >> p.fi; cin >> p.se;}
template<typename C> inline void _cout(const C &c){cout << c;}
template<typename T,typename U> inline void _cout(const pair<T,U> &p){cout << p.fi << ' ' << p.se;}
void in(){} template <typename T,class... U> void in(T &t,U &...u){ _cin(t); in(u...);}
void out(){cout << endl;} template <typename T,class... U> void out(const T &t,U ...u){ _cout(t); if(sizeof...(u)) cout << ' '; out(u...);}
template<typename C> inline void in(vector<C> &v,int N=-1){if(sz(v) != 0){int M=(N == -1) ? sz(v) : N; rep(i,M) _cin(v[i]);}else{C c;rep(i,N) v.pb((_cin(c),c));}}
template<typename C> inline void in(C v[],int N){rep(i,N) _cin(v[i]);}
template<typename C> inline void out(const vector<C> &v,int N=-1){int M=(N == -1) ? sz(v) : N; rep(i,M) {cout<<( (i)?" ":"" ); _cout(v[i]);} cout<<endl; }
template<typename C> inline void out(C v[],int N){rep(i,N) {cout<<( (i)?" ":"" ); _cout(v[i]);} cout<<endl; }
template<typename C> inline void vector_debug(const vector<C> &v,int N=-1){cout << "{"; int M=(N == -1) ? sz(v) : N; rep(i,M) {cout<<( (i)?", ":"" ); _cout(v[i]);} cout<<"}"; }
template<typename C> inline void vector_debug(C v[], int N){cout << "{"; rep(i,N) {cout<<((i)?", ":""); _cout(*(v+i));} cout<<"}\n";}
void dbg_out(){cout << endl;} template <typename T,class... U> void dbg_out(const T &t,U ...u){ _cout(t); if(sizeof...(u)) cout << ", "; dbg_out(u...);}
template<typename C,class... U> void dbg_out(const vector<C> &v,U ...u){vector_debug(v); if(sizeof...(u)) cout << ", "; dbg_out(u...);}
template<typename C,class... U> void dbg_out(const vector<vector<C>> &v,U ...u){cout << "{ "; rep(i,sz(v)) {if(i)cout<<", "; vector_debug(v[i]);} cout << " }"; if(sizeof...(u)) cout << ", "; dbg_out(u...);}
template<typename C> inline C vmax(const vector<C> &v){C n=v[0]; rep(i,sz(v)) amax(n,v[i]); return n;} template<typename C> inline C vmax(C v[], int N){C n=v[0]; rep( i , N ) amax(n,v[i]); return n;}
template<typename C> inline C vmin(const vector<C> &v){C n=v[0]; rep(i,sz(v)) amin(n,v[i]); return n;} template<typename C> inline C vmin(C v[], int N){C n=v[0]; rep( i , N ) amin(n,v[i]); return n;}
template<typename C> inline C vsum(const vector<C> &v){C n=0; rep(i,sz(v)) n+=v[i]; return n;} template<typename C> inline C vsum(C v[], int N){C n=0; rep( i , N ) n+=v[i]; return n;}

////////////
/// main ///
////////////

// Union-Find木
// 初期化 UF(N); Nは要素数
// 結合 unite(x,y); 同じ集合か判定 same(x,y);
struct UF{
    vector<int> par,sizes;
    UF(int N) : par(N),sizes(N, 1){ for(int i=0; i<N; i++) par[i]=i; }

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

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

    int size(int x){ return sizes[find(x)]; }

    void unite(int x, int y){
        x = find(x); y = find(y);
        if(x == y) return;
        if(sizes[x] < sizes[y]) swap(x,y);
        par[y] = x;
        sizes[x] += sizes[y];
    }
};

// 重み付きグラフ　テンプレート
struct edge{
    int src,to;
    int cost;
    edge(){}
    edge(int to,int cost): src(-1), to(to), cost(cost){}
    edge(int src,int to,int cost) : src(src), to(to), cost(cost){}
    edge& operator = (const int &x){ // edge e = n; とできる(e.to = n)
    to = x;
    return *this;
    }
    operator int() const{ return to; } // v[e]とできる ( v[e.to]に同じ )
};
bool operator <(const edge& e1,const edge& e2){
    return e1.cost < e2.cost;
}
using Edges = vector< edge >;
using WG = vector< Edges >;

//　Kruskal法 計算量は(E log(V))
template<typename T>
T kruskal(int V, int E,Edges& es){
    sort(all(es));
    UF uf(V);
    T res = 0;
    rep(i,E){
        edge e = es[i];
        if(!uf.same(e.src, e.to)){
            uf.unite(e.src, e.to);
            res += e.cost;
        }
    }
    return res;
}

int main(){
    ini(N);
    vpii px(N); vpii py(N);
    rep(i,N){
        ini(x,y);
        px[i] = mp(x,  i);
        py[i] = mp(y , i);
    }
    sort(all(px)); sort(all(py));
    Edges es;
    rep(i,N-1){
        es.pb( edge(px[i].se, px[i+1].se, px[i+1].fi - px[i].fi) );
        es.pb( edge(py[i].se, py[i+1].se, py[i+1].fi - py[i].fi) );
    }
    ll ans = kruskal<ll>(N, sz(es), es);
    out(ans);

}    


Measured memory_bytes: 6516