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

using namespace std;

#define MAX 300000

#define int long long

struct Pair{

	int x,y, id;

};

int n;

Pair a[MAX+1];

typedef Pair PP;

typedef pair<int,int> pp;

vector<pair<int,int> > G[MAX+1];

bool cmp(PP a,PP b){return a.x<b.x;};

bool CMP(PP a,PP b){return a.y<b.y;};

bool visited[MAX+1];

int ans;

#define fi first

#define se second

void DJK(int x){

	ans = 0;

	priority_queue<pp,vector<pp> ,greater<pp> >pq;

	pq.push({0,x});

	while(!pq.empty()){

		int u = pq.top().se;

		int w = pq.top().fi;

		pq.pop();

		if(visited[u]) continue;

		ans+=w;

		visited[u] = 1;

		for(pp ii : G[u]){

			int v = ii.se;

			pq.push({ii.fi,v});

		}

	}

}

signed main(){

	cin >> n;

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

		cin >> a[i].x >> a[i].y;

		a[i].id = i;

	}

	sort(a+1,a+n+1,cmp);

	for(int i=2;i<=n;i++){

		G[a[i].id].push_back({a[i].x-a[i-1].x,a[i-1].id});

		G[a[i-1].id].push_back({a[i].x-a[i-1].x,a[i].id});

	}

	sort(a+1,a+n+1,CMP);

	for(int i=2;i<=n;i++){

		G[a[i].id].push_back({a[i].y-a[i-1].y,a[i-1].id});

		G[a[i-1].id].push_back({a[i].y-a[i-1].y,a[i].id});

	}

	DJK(1);

	cout << ans;

}

// Faster C++ solution for the same problem (measured speedup: 2.3693738249810083x):
#include <bits/stdc++.h>

using namespace std;

#define ll long long

struct p {

	int x, y;

	int indx;

};

const int N = 1e5 + 5;

p points[N];

int n;

int par[N];

int get(int n) {

	if (par[n] == n) return n;

	return par[n] = get(par[n]);

}

vector<int> g[N];

void solve() {

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

		par[i] = i;

	vector<pair<int, pair<int, int> >> edg;

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

//		g[i].clear();

//		g[i].resize(n);

		for (int j = 0; j < g[i].size(); j++) {

//			g[i][j] = j;

			int v = g[i][j];

			ll c = min(abs(points[i].x - points[v].x),

					abs(points[i].y - points[v].y));

			edg.push_back(make_pair(c, make_pair(i, v)));

		}

	}

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

	ll ans = 0;

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

		int u = edg[i].second.first;

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

		int r1 = get(u);

		int r2 = get(v);

		if (r1 == r2) continue;

		//cout << u << "  " << v << endl;

		ans += edg[i].first;

		par[r1] = r2;

	}

	cout << ans << endl;

}

void gen(vector<pair<int, int> > &a, vector<pair<int, int> > &b) {



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



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



		auto it = lower_bound(b.begin(), b.end(), make_pair(a[i].first, -1));

		if (it != b.end()) {

			g[a[i].second].push_back(it->second);

			g[it->second].push_back(a[i].second);

		}

		if (it != b.begin()) {

			it--;



			g[a[i].second].push_back(it->second);

			g[it->second].push_back(a[i].second);

		}

	}

}

int main() {

	ios_base::sync_with_stdio(0);

	cin.tie(0);

	cin >> n;

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

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

		cin >> points[i].x >> points[i].y;

		points[i].indx = i;

		v.push_back(make_pair(points[i].x, make_pair(points[i].y, i)));

	}

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

	vector<pair<int, int> > last, cur;

	for (int i = 0; i < n;) {

		int X = v[i].first;

		while (i < n && v[i].first == X) {

			cur.push_back(v[i].second);

			i++;

		}

		if (last.size()) gen(last, cur);

		last = cur;

		cur.clear();

	}

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

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

		int V = v[i + 1].second.second;

		g[u].push_back(V);

		g[V].push_back(u);

	}

	for (int i = 0; i < n; i++)

		swap(v[i].first, v[i].second.first);

	last.clear();

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

	for (int i = 0; i < n;) {

		int X = v[i].first;



		while (i < n && v[i].first == X) {

			cur.push_back(v[i].second);

			i++;

		}

		if (last.size()) gen(last, cur);

		last = cur;

		cur.clear();

	}

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

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

		int V = v[i + 1].second.second;

		g[u].push_back(V);

		g[V].push_back(u);

	}



	solve();

	return 0;

}