#include <bits/stdc++.h>

#define rep(i,n) for(long long int (i)=0;(i)<(int)(n);(i)++)
#define rrep(i,a,b) for(long long int i=(a);i<(b);i++)
#define rrrep(i,a,b) for(long long int i=(a);i>=(b);i--)
#define all(v) (v).begin(), (v).end()
#define pb(q) push_back(q)
#define Abs(a,b) max(a,b)-min(a,b)
#define YES(condition) if(condition){cout << "YES" << endl;}else{cout << "NO" << endl;}
#define Yes(condition) if(condition){cout << "Yes" << endl;}else{cout << "No" << endl;}
#define Cout(x) cout<<(x)<<endl
#define POSSIBLE(condition) if(condition){cout << "POSSIBLE" << endl;}else{cout << "IMPOSSIBLE" << endl;}
#define Possible(condition) if(condition){cout << "Possible" << endl;}else{cout << "Impossible" << endl;}
#define possible(condition) if(condition){cout << "possible" << endl;}else{cout << "impossible" << endl;}
#define Size(n) (n).size()

typedef long long ll;


using namespace std;

const int INF = 1e9,MOD = 1e9 + 7;
const ll LINF = 1e18;

/*---------------------------------------------------------------
long long int kaizyo(long long int hh){
    cmp=1;
    while(hh>1){
        cmp=(cmp*hh)%MOD;
        hh--;
    }
    return cmp;
}
long long int ruizyo(long long int aa, long long int bb){
    if(aa==0){
        return 1;
    }
    else if(aa%2==0){
        long long int tt=ruizyo(aa/2,bb);
        return (tt*tt)%MOD;
    }
    else{
        return (ruizyo(aa-1,bb)*bb)%MOD;
    }
}フェルマ－のア
---------------------------------------------------------------

while(x!=0){
            sum+=x%10;
          / x/=10;
        }
        各桁の和
---------------------------------------------------------------

pair<int,int> p[100000];
cin >> tmp;
p[i]=make_pair(tmp,i);
cout << p[i].second+1 << endl;//ペアの右側つまりiを出力
---------------------------------------------------------------

s.find(w[i])==string::npos
findの使い方
---------------------------------------------------------------

for(int i=0;i<n;i++){
    b[i]=x%2;
    x/=2;
  }二進数
---------------------------------------------------------------

bool f[100001];//1000000以下の素数を調べよう！
rrep(i,2,100001){
       f[i]=false;
    }
rrep(i,2,100001){
        if(!f[i]){
            for(int j=i+i;j<=100000;j+=i){
                f[j]=true;
            }
        }
    }
    for(int i=3;i<=100000;i+=2){
        if(!f[i]){
            c[i]++;
        }
    }
---------------------------------------------------------------

visited=vector<vector<bool>>(10,vector<bool>(10,false));アを全部falseに
---------------------------------------------------------------

long long gcd(long long aaa,long long bbb){
    if(bbb==0){
        return aaa;
    }
    return gcd(bbb,aaa%bbb);
}
 
long long lcm(long long aaa,long long bbb){
    long long g = gcd(aaa,bbb);
    return aaa/g * bbb;
}左から最大公約数と最小公倍数


---------------------------------------------------------------

long long int prime_cnt[10000];
       for(int i=2;i*i<=n;i++){
           while(n%i==0){
               n/=i;
               prime_cnt[i]+=1;
           }
           if(n>1){
               prime_cnt[n]+=1;
               break;
           }
      }ある数nを素因数分解しましょう
---------------------------------------------------------------*/

long long int n,cnt=0,ans=0,a,b,c,d,cmp,cmpp,m,h,w,sum=0,pos,par[1000000],ran[1000000];
int dy[]={1,0,-1,0};
int dx[]={0,1,0,-1};
string alph("abcdefghijklmnopqrstuvwxyz"),s;
bool fl=true;
struct edge{ll from,to,cost;};
edge g[1000000];

//-------------------------↓↓↓↓↓↓------------------------

void init(ll nn){
        rep(i,nn){
            par[i]=i;
            ran[i]=0;
        }
}

ll root(ll xx){
    if(par[xx]==xx)return xx;
    else return par[xx]=root(par[xx]);
}

bool same(ll xx,ll yy){
    return root(xx)==root(yy);
}

void unite(ll xx,ll yy){
    xx=root(xx);
    yy=root(yy);
    if(xx==yy)return;
    if(ran[xx]<ran[yy])par[xx]=yy;
    else{
        par[yy]=xx;
        if(ran[xx]==ran[yy])ran[xx]++;
    }
}

bool comp(const edge& e1, const edge& e2){
    return e1.cost<e2.cost;
}

ll kruskal(){
    sort(g,g+2*n,comp);
    init(2*n);
    ll res=0;
    rep(i,2*n){
        edge e=g[i];
        if(!same(e.from,e.to)){
            unite(e.from,e.to);
            res+=e.cost;
        }
    }
    return res;
}

int main(void){
       cin.tie(0);
    ios::sync_with_stdio(false);

       cin >> n;
       vector<pair<ll,ll> > x;
       vector<pair<ll,ll> > y;
       rep(i,n){
           cin>>a>>b;
           x.push_back({a,i});
           y.push_back({b,i});
       }
       sort(all(x));
       sort(all(y));
       rep(i,n-1){
           g[i]={x[i].second,x[i+1].second,x[i+1].first-x[i].first};
           g[n+i]={y[i].second,y[i+1].second,y[i+1].first-y[i].first};
       }
       Cout(kruskal());
return 0;
}


Measured memory_bytes: 17892