#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <cctype>
#include <cassert>
#include <climits>
#include <string>
#include <bitset>
#include <cfloat>
#include <unordered_set>
#include <iomanip>
using namespace std;
typedef long double ld;
typedef long long int ll;
typedef unsigned long long int ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<char> vc;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef vector<string> vs;
typedef vector<ll> vll;
typedef vector<pair<int,int> > vpii;
typedef vector<vector<int> > vvi;
typedef vector<vector<char> > vvc;
typedef vector<vector<string> > vvs;
typedef vector<vector<ll> > vvll;
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define irep(it, stl) for(auto it = stl.begin(); it != stl.end(); it++)
#define drep(i,n) for(int i = (n) - 1; i >= 0; --i)
#define fin(ans) cout << (ans) << endl
#define mp(p,q) make_pair(p, q)
#define pb(n) push_back(n)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define Sort(a) sort(a.begin(), a.end())
#define Rort(a) sort(a.rbegin(), a.rend())
#define MATHPI acos(-1)
int dx8[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy8[8] = {0, 1, 0, -1, 1, 1, -1, -1};
int dx4[4] = {1, 0, -1, 0};
int dy4[4] = {0, 1, 0, -1};
template <class T> inline bool chmax(T& a,T b){if(a<b){a=b;return 1;} return 0;}
template <class T> inline bool chmin(T& a,T b){if(a>b){a=b;return 1;} return 0;}
struct io{io(){ios::sync_with_stdio(false);cin.tie(0);}};
const int INF = INT_MAX;
const ll LLINF = 1LL<<60;
const ll MOD = 1000000007;
const double EPS = 1e-9;

struct UnionFind {  
vector<int> par,rank; 
UnionFind(int n) : par(n),rank(n,1)  {
 for(int i=0; i<n; i++){ par[i]=i; }
}
int find(int x) { 
if(par[x]==x){ return x; }
return par[x] = find(par[x]);
}
void unite(int x, int y) {
int rx = find(x); 
int ry = find(y);
if(rx == ry){ return; }
if(rank[rx]<rank[ry]){ swap(rx, ry); }
par[ry] = rx;
rank[rx] += rank[ry];
}
bool isSame(int x, int y) { 
return find(x) == find(y);
}
int size(int x){
return rank[find(x)];
}
};
struct edge {
int u;
int v;
int cost;
};
vector<edge> es;
bool comp(const edge& e1, const edge& e2) {
return e1.cost < e2.cost;
}

struct cor{
    int x,y,idx;
};

int main(void) {
    int N; cin >> N;
    //やりたいことは全部にedgeを張ってはいられないので、xでソートして隣接しているところだけ、yも同様に

    //x,yは10^9なのでllを使おう
    vector<cor> corVec;
    rep(i,N){
        int x,y;
        cin >> x >> y;
        cor t;
        t.x = x; t.y = y; t.idx=i;
        corVec.emplace_back(t);
    }
    
    //xでソートしてedgeに入れる
    sort(corVec.begin(),corVec.end(),[&](cor c1,cor c2){return c1.x < c2.x;});
    rep(i,N-1){
        int cost = abs(corVec[i].x - corVec[i+1].x);
        es.push_back({corVec[i].idx,corVec[i+1].idx,cost});
    }
    //yでソートしてedgeに入れる
    sort(corVec.begin(),corVec.end(),[&](cor c1,cor c2){return c1.y < c2.y;});
    rep(i,N-1){
        int cost = abs(corVec[i].y - corVec[i+1].y);
        es.push_back({corVec[i].idx,corVec[i+1].idx,cost});
    }
    
    //x,yごちゃまぜにして隣接した小さい奴からつないでいく
    sort(es.begin(),es.end(),comp);
    UnionFind uf(N);

    ll ans=0;
    for(auto e:es){
        if(uf.isSame(e.u,e.v))continue;
        uf.unite(e.u,e.v);
        ans+=e.cost;
    }
    fin(ans);
    
}

Measured memory_bytes: 6132