/*
                                                                                                     
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                                          `-+o+/:---:/+o/.                                          
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                                               ``````                                               
*/


#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <set>
#include <queue>
#include <ostream>
#include <istream>
#include <typeinfo>
#include <iomanip>
#include <cstdio>
#include <cstdlib>
#include <cassert>
#include <limits>
#include <fstream>
#include <array>
#include <list>
#include <bitset>
#include <functional>

#define mt make_tuple
#define x first
#define y second
#define pb push_back
#define ppb pop_back
#define pf push_front
#define ppf pop_front
#define mp make_pair
#define umap unordered_map
#define uset unordered_set
#define rt return 0;
#define elif else if
#define len(v) ((int)v.size())


using namespace std;

char string_in_buffer[(int)260];


void fast_scan(int &x) { scanf("%d", &x); }
void fast_scan(long long &x) { scanf("%lld", &x); }
void fast_scan(unsigned long long &x) { scanf("%llu", &x); }
void fast_scan(double &x) { scanf("%lf", &x); }
void fast_scan(long double &x) { scanf("%Lf", &x); }
void fast_scan(char &x) { 
	scanf("%c", &x); 
	if (x == '\n') {
		fast_scan(x);
	}
}
void fast_scan(string &x) {
	scanf("%s", string_in_buffer);
	x = string(string_in_buffer);
}

template<class TFirst, class TSecond>
void fast_scan(pair<TFirst, TSecond> &p) {
	fast_scan(p.first);
	fast_scan(p.second);
}

template <class T>
void fast_scan(vector<T> &v) {
	for (auto &x : v) fast_scan(x);
}

void fast_print(const int &x) { printf("%d", x); }
void fast_print(const long long &x) { printf("%lld", x); }
void fast_print(const unsigned long long &x) { printf("%llu", x); }
void fast_print(const double &x) { printf("%.15lf", x); }
void fast_print(const long double &x) { printf("%.15Lf", x); }
void fast_print(const char &x) { printf("%c", x); };
void fast_print(const string &x) { printf("%s", x.c_str());}

template<class TFirst, class TSecond>
void fast_print(const pair<TFirst, TSecond> &p) {
	fast_print(p.first);
	fast_print(' ');
	fast_print(p.second);
}

template <class T>
void fast_print(const vector<T> &v) {
	if (v.empty()) return;
	fast_print(v[0]);
	for (int i = 1; i < v.size(); i++) {
		fast_print(" ");
		fast_print(v[i]);
	}
}

template <class T>
void fast_print(const vector<vector<T>> &v) {
	if (v.empty()) return;
	fast_print(v[0]);
	for (int i = 1; i < v.size(); i++) {
		fast_print("\n");
		fast_print(v[i]);
	}
}



using namespace std;


namespace smart_io {
	string print_start = "";
	string sep = " ";
	bool first_print = false;

	void precall_print() {
		fast_print(print_start);
		print_start = "\n";
		first_print = true;
	}
} //namespace smart_io


template <class T>
ostream &operator,(ostream &os, const T &object) {
	if (!smart_io::first_print) {
		fast_print(smart_io::sep);
	} else {
		smart_io::first_print = false;
	}
	fast_print(object);
	return os;
}

template <class T>
istream &operator,(istream &is, T &object) {
	fast_scan(object);
	return is;
}

namespace typedefs {
	typedef long long ll;
	typedef unsigned long long ull;
	typedef pair<int, int> pii;
}

namespace numbers_operation {
	template<class T>
	T floor_mod(T a, T b) {
		if (a % b == 0) return 0;
		if (a >= 0 && b >= 0) return a % b;
		if (a <= 0 && b <= 0) return a % b;
		return abs(b) - (abs(a) % abs(b));
	}
}

using namespace numbers_operation;
using namespace typedefs;

#define print    \
smart_io::precall_print(); \
cout,

#define scan cin,

int n;
vector<pair<int, int>> v;


struct SUS {
	vector<int> up;

	SUS(int n) {
		up.resize(n);
		for (int i = 0; i < n; i++) {
			up[i] = i;
		}
	}

	int get_root(int v) {
		if (up[v] == v) return v;
		return up[v] = get_root(up[v]);
	}

	void merge(int a, int b) {
		a = get_root(a);
		b = get_root(b);
		up[a] = b;
	}

	bool one_comp(int a, int b) {
		return get_root(a) == get_root(b);
	}
};

struct Edge {
	int a, b;
	int productivity;

	Edge() {}

	Edge(int _a, int _b, int _prod) {
		a = _a;
		b = _b;
		productivity = _prod;
	}
};

signed main(signed argc, char *argv[]) {
	scan n;
	v.resize(n);
	scan v;

	vector<pii> xcord;
	vector<pii> ycord;

	for (int i = 0; i < n; i++) {
		xcord.emplace_back(v[i].x, i);
		ycord.emplace_back(v[i].y, i);
	}

	sort(xcord.begin(), xcord.end());
	sort(ycord.begin(), ycord.end());

	vector<Edge> edges;
	for (int i = 0; i < len(xcord) - 1; i++) {
		edges.emplace_back(xcord[i].second, xcord[i + 1].second, xcord[i + 1].first - xcord[i].first);
	}
	for (int i = 0; i < len(ycord) - 1; i++) {
		edges.emplace_back(ycord[i].second, ycord[i + 1].second, ycord[i + 1].first - ycord[i].first);	
	}

	sort(edges.begin(), edges.end(), [](Edge a, Edge b){
		return a.productivity < b.productivity;
	});

	SUS sus(n);
	ll total = 0;
	for (Edge e : edges) {
		if (sus.one_comp(e.a, e.b)) continue;
		sus.merge(e.a, e.b);
		total += e.productivity;
	}
	print total;
}

Measured memory_bytes: 7912