// Slower C++ solution:
#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;

}


// Faster C++ solution for the same problem (measured speedup: 3.902611279818304x):
#pragma GCC optimize ("O3")

#include <bits/stdc++.h>

using namespace std;

#define MuhammedAly ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);

#define all(x) (x).begin(),(x).end()

#define allr(x) (x).rbegin(),(x).rend()

#define pb push_back

#define eb emplace_back

#define popc(x) __builtin_popcount(x)

#define LLMX 1e18

#define NotinRange(n,m) i<0||i>=(n)||j<0||j>=(m)

#define mem(x,y) memset((x),(y),sizeof (x));

#define sz(a) (int)(a).size()

#define inFile(s) freopen((s),"r",stdin)

#define	outFile(s) freopen((s),"w",stdout)

#define biEdge(v, a, b) (v)[(a)].pb((b)), (v)[(b)].pb((a))

#define pi (2 * acos(0))

#define X real()

#define Y imag()

#define cross(a, b) ((conj(a) * (b)).Y)

#define dot(a, b) ((conj(a) * (b)).X)

#define vec(a,b) ((b) - (a))

#define ll long long

typedef long double ld;

typedef complex<double>point;

typedef tuple<int, int, int> line;

typedef pair<point, point>segment;

typedef vector<point>polygon;

const int N = 1e5 + 5, M = 100 + 5, OO = 0x3f3f3f3f, mod = 1e9 + 7, base = 131, mod2 = 1000136437, mod3 = 998244353;

const double EPS = 1e-9;

int n, rp[N], si[N];

ll ans;

vector<pair<int, pair<int, int>>>x, y;

map<int, vector<pair<int, int>>> mp;

int find(int u)

{

	return (rp[u] == u)? u : rp[u] = find(rp[u]);

}

bool join(int u, int v)

{

	u = find(u), v = find(v);

	if(u == v)

		return false;

	if(si[u] < si[v])

		swap(u, v);

	si[u] += si[v];

	rp[v] = u;

	return true;

}

int main()

{

    MuhammedAly

    cin >> n;

    fill(si, si + n + 1, 1);

    iota(rp, rp + n + 1, 0);

    x.resize(n);

    y.resize(n);

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

    {

    	cin >> x[i].first >> x[i].second.first;

    	y[i].first = x[i].second.first;

    	y[i].second.first = x[i].first;

    	x[i].second.second = y[i].second.second = i;

    }

    sort(all(x));

    sort(all(y));

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

    {

    	mp[x[i + 1].first - x[i].first].pb({x[i].second.second, x[i + 1].second.second});

    	mp[y[i + 1].first - y[i].first].pb({y[i].second.second, y[i + 1].second.second});

    }

    for(auto i : mp)

    {

    	for(auto j : i.second)

    		if(join(j.second, j.first))

    			ans += i.first;

    }

    cout << ans;

    return 0;

}