// Slower C++ solution:
#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/tree_policy.hpp>



using namespace std;

using namespace __gnu_pbds;



#define fi first

#define se second

#define mp make_pair

#define pb push_back

#define fbo find_by_order

#define ook order_of_key



typedef long long ll;

typedef pair<ll,ll> ii;

typedef vector<int> vi;

typedef long double ld;

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;

bool marked[100001];

vector<ii> v[100001];  //adjList



ll prim(int k){

    priority_queue<ii, vector<ii>, greater<ii> > q;

    ll u;

    long long minimumCost = 0;

    ii p;

    q.push(mp(0, k));

    while(!q.empty())

    {

        p = q.top();

        q.pop();

        k = p.second;

        if(marked[k] == true)

            continue;

        minimumCost += p.fi;

        marked[k] = true;

        for(ll i = 0;i < v[k].size();++i)

        {

            u = v[k][i].se;

            if(marked[u] == false)

                q.push(v[k][i]);

        }

    }

    return minimumCost;

}



int main() {

    std::ios::sync_with_stdio(false);

    cin.tie(NULL);

    long long n;

    cin>>n;

    vector<ii> x;

    vector<ii> y;

    for(ll i =0;i<n;i++){

        ll a,b;

        cin>>a>>b;

        x.pb(mp(a,i));

        y.pb(mp(b,i));

    }

    sort(x.begin(),x.end());

    sort(y.begin(),y.end());

    for(ll i=0;i<n-1;i++){

        v[x[i].se].pb(mp(x[i+1].fi-x[i].fi,x[i+1].se));

        v[x[i+1].se].pb(mp(x[i+1].fi-x[i].fi,x[i].se));

        v[y[i].se].pb(mp(y[i+1].fi-y[i].fi,y[i+1].se));

        v[y[i+1].se].pb(mp(y[i+1].fi-y[i].fi,y[i].se));

    }

    ll ans=prim(0);

    cout<<ans;

    return 0;

}


// Faster C++ solution for the same problem (measured speedup: 2.5298021480163784x):
#include<bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5 ;

int p[N],n ;

int rnk[N];

vector < pair < int , pair < int , int > > > v;

int parent(int x){

   if(p[x] == x)

       return x;

   return p[x] = parent(p[x]);

}

bool isConnected(int x , int y){

   return parent(x) == parent(y);

}

void connect(int x , int y){

   if(isConnected(x,y))

       return;

   int pOfx = parent(x);

   int pOfy = parent(y);

   if(rnk[pOfx] > rnk[pOfy]){

       p[pOfy] = pOfx;

   }else if(rnk[pOfy] > rnk[pOfx]){

       p[pOfx] = pOfy;

   }else{

       p[pOfy] = pOfx;

       rnk[pOfx]++;

   }

}

void preDSU(){

   for(int i = 0;i<N;i++){

       p[i] = i;

   }

}



int main(){

    preDSU();

    scanf("%d",&n);

    vector < pair < int ,int > > v1, v2;

    for(int i = 1 ; i <= n ; i++){

        int x,  y;

        scanf("%d%d",&x,&y);

        v1.push_back({x,i});

        v2.push_back({y,i});

    }

    sort(v1.begin(),v1.end());

    sort(v2.begin(),v2.end());

    for(int i = 1 ; i < n ; i++){

        v.push_back({v1[i].first - v1[i - 1].first,{v1[i].second,v1[i - 1].second}});

        v.push_back({v2[i].first - v2[i - 1].first,{v2[i].second,v2[i - 1].second}});

    }

    sort(v.begin(),v.end());

    long long ans = 0 ;

    for(int i = 0 ; i < v.size() ; i++){

        int x = v[i].second.first;

        int y = v[i].second.second;

        long long cost = v[i].first;

        if (isConnected(x, y))

            continue;

        connect(x,y);

        ans += cost;

    }

    cout << ans;

    return 0;

}