#define _USE_MATH_DEFINES
#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <string>
#include <vector>
#include <utility>
#include <complex>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <deque>
#include <tuple>
#include <bitset>
#include <limits>
#include <algorithm>
#include <array>
#include <random>
#include <complex>
#include <regex>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()	{cin.tie(0);	cout.sync_with_stdio(false);}
#define reach(i,a)	for(auto i:a)
#define rep(i,n)	for(int i=0;i<(int)n;i++)
#define REP(i,n)	for(int i=0;i<=(int)n;i++)
#define srep(i,a,n)	for(int i=a;i<(int)n;i++)
#define SREP(i,a,n)	for(int i=a;i<=(int)n;i++)
#define rrep(i,n)	for(int i=n-1;i>=0;i--)
#define RREP(i,n)	for(int i=n;i>=0;i--)
#define all(a)	(a).begin(),(a).end()
#define mp(a,b)	make_pair(a,b)
#define mt	make_tuple
#define pb	push_back
int bitcnt(ll x) {
	x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
	x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
	x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
	x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
	x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
	x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
	return x;
}
int bitcnt(int x) {
	x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
	x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
	x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
	x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
	x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
	return x;
}
ll sqrtll(ll x) {
	ll left = 0, right = x;
	rep(i, 100) {
		ll mid = (left + right) >> 1;
		if (mid*mid <= x)	left = mid;
		else	right = mid;
	}
	return left;
}
ll gcd(ll a, ll b) {
	return a%b == 0 ? b : gcd(b, a%b);
}
#define debug(x)	printf("Case #%d: ", x)
#define DEBUG 0
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ld eps = 1e-9;
const int dx[] = { 1,0,-1,0,0 };
const int dy[] = { 0,1,0,-1,0 };

// Union-Find
int group[100010];
int findparent(int i) {
	return group[i] = (i == group[i] ? i : findparent(group[i]));
}
void merge(int i, int j) {
	i = findparent(i);
	j = findparent(j);
	group[i] = j;
}

int main() {
	int n;	cin >> n;
	vector<pair<ll, ll>> p(n);
	rep(i, n) cin >> p[i].first >> p[i].second;
	// x,yだけの値のリストを作る(idもついていると楽)
	vector<pair<ll, int>> x(n), y(n);
	rep(i, n) {
		x[i] = mp(p[i].first, i);
		y[i] = mp(p[i].second, i);
	}
	sort(all(x));	sort(all(y));
	// 辺
	vector<tuple<ll, int, int>> edge;
	srep(i, 1, n) {
		// xの隣接した頂点をつなぐ
		edge.push_back(mt(labs(x[i].first - x[i - 1].first), x[i].second, x[i - 1].second));
		// yも同様
		edge.push_back(mt(labs(y[i].first - y[i - 1].first), y[i].second, y[i - 1].second));
	}
	// 辺の重みが軽い順に並べる
	sort(all(edge));
	// クラスカル法。Union-Findを使います。
	ll ret = 0;
	rep(i, n)	group[i] = i;
	for (auto e : edge) {
		ll weight;	int a, b;
		tie(weight, a, b) = e;
		if (findparent(a) != findparent(b)) {
			merge(a, b);
			ret += weight;
		}
	}
	cout << ret << endl;
	return 0;
}

Measured memory_bytes: 11120