#pragma region Template
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cstdlib>
#include <queue>
#include <vector>
#include <map>
#include <cmath>
#include <string>
#include <cstring>
#include <utility>
#include <stack>
#include <set>
#include <algorithm>
#include <bitset>
#include <functional>
#include <ctime>
#include <cassert>
#include <valarray>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <complex>
#include <regex>
#pragma comment(linker, "/STACK:167772160")

using namespace std;
#define mp make_pair
#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#define print_var(x) cerr << #x << " : " << (x) << endl
#define print_array(arr, len) {cerr << #arr << " : "; for(int i = 0; i < len; ++i) cerr << arr[i] << ' '; cerr << endl;}
#define print_2d_array(arr, len1, len2) {cerr << #arr << endl; for(int i = 0; i < len1; ++i, cerr << endl) for(int j = 0; j < len2; ++j) cerr << arr[i][j] << ' ';}
#define print_iterable(i) {cerr << #i << " : "; for(auto e : i) cerr << e << ' '; cerr << endl;}
#define print_new_line() cerr << endl

template <typename T, typename Q>
void print_pair1(pair<T, Q> x)
{
	cerr << "(" << x.first << ", " << x.second << ")\n";
}

#define print_pair(x) {cerr << #x << " : "; print_pair1(x);}
#else
#define print_pair(x) (void)0
#define eprintf(...) (void)0
#define print_var(x) (void)0
#define print_array(arr, len) {}
#define print_2d_array(arr, len1, len2) {}
#define print_iterable(i) {}
#define print_new_line() (void)0
#endif

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef unsigned int uint;
typedef pair<int, int> pii;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;

const int INF = (int)1e9 + 10;
const ll LINF = ll(2e18) + 10;
const double PI = acosl(-1);
const double eps = 1e-8;
const ld EPS = 1e-12;
#pragma endregion

#ifdef LOCAL
#define ERR_CATCH
//#define NOERR
#endif

const int N = 1e5 + 10;

struct DSU
{
	int rank[N];
	int anc[N];
	DSU() : rank()
	{
		for (int i = 0; i < N; ++i)
			anc[i] = i;
	}
	int get(int x)
	{
		return x == anc[x] ? x : anc[x] = get(anc[x]);
	}
	bool unite(int a, int b)
	{
		a = get(a);
		b = get(b);
		if (a == b)
			return false;
		if (rank[a] < rank[b])
			swap(a, b);
		if (rank[a] == rank[b])
			++rank[a];
		anc[b] = a;
		return true;
	}
} dsu;

int n;
pii x[N], y[N];

struct Rec
{
	int cost;
	int a, b;
	Rec(int cost, int a, int b) : cost(cost), a(a), b(b) {}
	bool operator< (const Rec& r) const
	{
		return cost < r.cost;
	}
};

void solve()
{
	scanf("%d", &n);
	for (int i = 0; i < n; ++i)
	{
		scanf("%d%d", &x[i].first, &y[i].first);
		x[i].second = y[i].second = i;
	}
	sort(x, x + n);
	sort(y, y + n);
	vector<Rec> recs;
	for (int i = 1; i < n; ++i)
	{
		recs.emplace_back(x[i].first - x[i - 1].first, x[i].second, x[i - 1].second);
		recs.emplace_back(y[i].first - y[i - 1].first, y[i].second, y[i - 1].second);
	}
	sort(recs.begin(), recs.end());
	int cnt = 1;
	ll ans = 0;
	for(auto r : recs)
		if (dsu.unite(r.a, r.b))
		{
			ans += r.cost;
			++cnt;
		}
	if (cnt != n)
		throw;
	printf("%lld\n", ans);
}

int main()
{
#ifdef LOCAL
	freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
#ifdef NOERR
	freopen("err.txt", "w", stderr);
#endif
#else
	//freopen("sum.in", "r", stdin);
	//freopen("sum.out", "w", stdout);
#endif

#ifdef ERR_CATCH
	try
	{
#endif

#ifdef ST
		while (true)
			solve();
#endif
#ifdef CASES
#define MULTITEST
#endif
#ifdef MULTITEST
		int t;
		scanf("%d", &t);
		char endl1[5];
		fgets(endl1, 5, stdin);
		for (int i = 0; i < t; ++i)
		{
#ifdef CASES
			printf("Case #%d: ", i + 1);
#endif
			solve();
#ifdef CASES
			eprintf("Passed case #%d:\n", i + 1);
#endif
		}
#else
		solve();
#endif

#ifdef ERR_CATCH
	}
	catch (logic_error e)
	{
		print_var(e.what());
		puts("___________________________________________________________________________");
		exit(0);
	}
#endif
#ifdef LOCAL
	eprintf("\n\nTime: %.3lf\n", double(clock()) / CLOCKS_PER_SEC);
#endif
}

Measured memory_bytes: 7284