#include "bits/stdc++.h"
using namespace std;
#define Rep(i,n) for(int i=0;i<(int)(n);i++)
#define For(i,n1,n2) for(int i=(int)(n1);i<(int)(n2);i++)
#define REP(i,n) for(ll i=0;i<(ll)(n);i++)
#define RREP(i,n) for(ll i=((ll)(n)-1);i>=0;i--)
#define FOR(i,n1,n2) for(ll i=(ll)(n1);i<(ll)(n2);i++)
#define RFOR(i,n1,n2) for(ll i=((ll)(n1)-1);i>=(ll)(n2);i--)
#define all(a)  (a).begin(),(a).end()
#define SORT(a) sort((a).begin(),(a).end())
#define oorret 0
#define oor(x) [&](){try{x;} catch(const out_of_range& oor){return oorret;} return x;}()
#define IOS cin.tie(0),ios::sync_with_stdio(false)
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
template<typename T1, typename T2> inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return 1; }return 0; }
template<typename T1, typename T2> inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return 1; }return 0; }
template<class Type>struct is_vector : std::false_type {};
template<class ValueType, class Alloc>struct is_vector<std::vector<ValueType, Alloc>> : std::true_type {};
template <typename T> inline ostream& operator << (ostream& out, const vector<T>& v) {
	if (v.empty())return out;
	constexpr bool is_vector_v = is_vector<T>::value;
	if (is_vector_v)for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? "\n" : "");
	else for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? " " : "");
	return out;
}
inline void put() {}
template<class T> inline void put(const T& first) { std::cout << first << "\n"; }
template<class T, class... N> inline void put(const T& first, const N& ... rest) { std::cout << first << " "; put(rest...); }
inline void putn() {}
template<class T, class... N> inline void putn(const T& first, const N& ... rest) { std::cout << first << "\n"; putn(rest...); }

template<class T>
struct edge {
	int from, to;
	T cost;
	edge(int from,int to,T cost):from(from),to(to),cost(cost){}
};



int main() {
	IOS;
	int n;
	cin >> n;
	vector<ll> x(n), y(n);
	vector<P> px(n), py(n);
	REP(i, n) {
		cin >> x[i] >> y[i];
		px[i].first = x[i];
		px[i].second = i;
		py[i].first = y[i];
		py[i].second = i;
	}
	sort(all(px));
	sort(all(py));
	using el = edge<ll>;
	vector<vector<el>> path(n);
	REP(i, n - 1) {
		int from1 = px[i].second;
		int to1 = px[i + 1].second;
		ll cost1 = min<ll>(abs(x[from1] - x[to1]), abs(y[from1] - y[to1]));
		el e1(from1, to1, cost1);
		int from2 = px[i + 1].second;
		int to2 = px[i].second;
		ll cost2 = min<ll>(abs(x[from2] - x[to2]), abs(y[from2] - y[to2]));
		el e2(from2, to2, cost2);
		path[from1].push_back(e1);
		path[from2].push_back(e2);
	}
	REP(i, n - 1) {
		int from1 = py[i].second;
		int to1 = py[i + 1].second;
		ll cost1 = min<ll>(abs(x[from1] - x[to1]), abs(y[from1] - y[to1]));
		el e1(from1, to1, cost1);
		int from2 = py[i + 1].second;
		int to2 = py[i].second;
		ll cost2 = min<ll>(abs(x[from2] - x[to2]), abs(y[from2] - y[to2]));
		el e2(from2, to2, cost2);
		path[from1].push_back(e1);
		path[from2].push_back(e2);
	}
	auto comp = [](el r, el l) {
		return r.cost > l.cost;
	};
	priority_queue<edge<ll>, vector<el>, decltype(comp)> pq{ comp };
	int source = 0;
	REP(i, path[source].size()) {
		pq.push(path[source][i]);
	}
	vector<el> mst;
	vector<bool> visited(n, false);
	visited[0] = true;
	
	ll res = 0;
	REP(i, n - 1) {
		bool flag = true;
		while (flag) {
			auto p = pq.top();
			pq.pop();
			if (!visited[p.to]) {
				REP(j, path[p.to].size()) {
					pq.push(path[p.to][j]);
				}
				visited[p.to] = true;
				flag = false;
				res += p.cost;
			}
		}
	}
	put(res);
	return 0;
}


Measured memory_bytes: 22256