//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
//#pragma GCC optimize("unroll-loops")
/*#pragma GCC optimize("section-anchors")
#pragma GCC optimize("profile-values,profile-reorder-functions,tracer")
#pragma GCC optimize("vpt")
#pragma GCC optimize("rename-registers")
#pragma GCC optimize("move-loop-invariants")
#pragma GCC optimize("unswitch-loops")
#pragma GCC optimize("function-sections")
#pragma GCC optimize("data-sections")
#pragma GCC optimize("branch-target-load-optimize")
#pragma GCC optimize("branch-target-load-optimize2")
#pragma GCC optimize("btr-bb-exclusive")*/
//#pragma comment(linker, "/STACK:367077216")
#define _CRT_SECURE_NO_WARNINGS
#include <chrono>
#include <set>
#include <map>
#include <deque>
#include <string>
#include <cstdint>
#include <cmath>
#include <queue>
#include <cassert>
#include <random>
#include <bitset>
#include <iomanip>
#include <numeric>
#include <time.h>//////////////
#include <ctime>
#include <string>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
//#define endl '\n'
#define mp make_pair
#define pbc push_back
#define pob pop_back()
#define empb emplace_back
#define queuel queue<long long>
#define sqr(a) ((a) * (a))
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define pin(p) cin >> p.first >> p.second;
#define uniq(a) sort(all(a));(a).resize(unique(all(a)) - a.begin());
#define rev(v) reverse(v.begin(), v.end());
#define sout(s, c) for (auto i : s) cout << i << c;
#define pout(p) cout << p.first << " " << p.second;
#define er(v, l, r) erase(v.begin() + l, v.begin() + r);
#define vin(v) for (ll i = 0; i < v.size(); ++i) cin >> v[i];
#define vout(v, c) for (int i = 0; i < v.size(); ++i) cout << v[i] << c;
#define pushi(v, a) for (int i = 0; i < a.size(); ++i) v.push_back(a[i]);
#define fastio() ios_base::sync_with_stdio(0); cout.tie(0); cin.tie(0); srand(time(NULL))
#define dab(v) for(auto i:v)cout<<i<<' ';
#define sp system("pause")
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
using namespace std;
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
const ld EPS = 0.001;
const ld EPS2 = 1e-6;
const ld PI = acos(-1);
const int MOD7 = 1000000007;
const int MOD9 = 1000000009;
const int a228 = 18;
const int inf = 1e9;
const ll kekmod = 1791791791;
const ll bestmod = 1148822869;
const int mod = MOD7;
const int MAXN = 2e5 + 1;
int p[MAXN];
int rnk[MAXN];
void make(int v)
{
	p[v] = v, rnk[v] = 0;
}
int fin(int v)
{
	return(p[v] == v ? v : p[v] = fin(p[v]));
}
void unite(int a, int b)
{
	a = fin(a), b = fin(b);
	if (a == b)return;
	if (rnk[a] < rnk[b])swap(a, b);
	p[b] = a;
	rnk[a] += (rnk[a] == rnk[b]);
}
struct edge
{
	int a, b, c;
};
bool cmp(edge a, edge b)
{
	return a.c < b.c;
}
signed main()
{
	fastio();
	int n;
	cin >> n;
	vector<pair<pair<int, int>,int>> a(n);
	for (int i = 0; i < n; ++i) cin >> a[i].first.first >> a[i].first.second;
	for (int i = 0; i < n; ++i) a[i].second = i;
	sort(all(a));
	vector<edge> e;
	for (int i = 0; i < n - 1; ++i)
	{
		e.pbc({ a[i].second, a[i + 1].second, a[i + 1].first.first - a[i].first.first });
	}
	sort(all(a), [&](pair<pair<int, int>, int> a, pair<pair<int, int>, int> b) { return a.first.second < b.first.second; });
	for (int i = 0; i < n - 1; ++i) e.pbc({ a[i].second, a[i + 1].second, a[i + 1].first.second - a[i].first.second });
	for (int i = 0; i < n; ++i) make(i);
	sort(all(e), cmp);
	ll ans = 0;
	for (auto j : e)
	{
		if (fin(j.a) != fin(j.b))
		{
			ans += j.c;
			unite(j.a, j.b);
		}
	}
	cout << ans;
	//sp;
}

Measured memory_bytes: 6132