// 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: 9.246745015477124x):
#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;

}