#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
//#define int long long
using bll = boost::multiprecision::cpp_int;
using ll = long long;
//constexpr int INF = 1e9;//INT_MAX=(1<<31)-1=2147483647
constexpr ll INF = (ll)1e18;//(1LL<<63)-1=9223372036854775807
constexpr ll MOD = (ll)1e9 + 7;
constexpr double EPS = 1e-9;
constexpr int dx[4]={1,0,-1,0};
constexpr int dy[4]={0,1,0,-1};
#define p(var) std::cout<<var<<std::endl
#define PI (acos(-1))
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define all(v) (v).begin(), (v).end()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end());
template<typename T> inline void pv(vector<T> v) { for(ll i=0, N=v.size(); i<N; i++) cout<< v[i] << (i==N-1 ? '\n' : ' '); }
template<typename T> inline T gcd(T a, T b) { return b ? gcd(b,a%b) : a; }
template<typename T> inline T lcm(T a, T b) { return a / gcd(a,  b) * b; }
template<typename T1, typename T2> inline T1 power(T1 x, T2 n){ return n ? power(x*x%MOD,n/2)*(n%2?x:1)%MOD : 1; }
template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
template<typename T> class dvector : public std::vector<T> {
public:
	dvector() : std::vector<T>() {}
	explicit dvector(size_t n, const T& value = T()) : std::vector<T>(n,value) {}
	dvector(const std::vector<T>& v) : std::vector<T>(v) {}
	dvector(const std::initializer_list<T> il) : std::vector<T>(il) {}
	dvector(const typename std::vector<T>::iterator first, const typename std::vector<T>::iterator last) : std::vector<T>(first, last) {}
	dvector(const std::string::iterator first, const std::string::iterator last) : std::vector<T>(first, last) {}
	T& operator[](size_t n) { return this->at(n); }
	const T& operator[](size_t n) const { return this->at(n); }
};
class dbool{
public:
	dbool() : boolvalue(false) {}
	dbool(bool b) : boolvalue(b) {}
	dbool(const dbool &b) : boolvalue(b.boolvalue) {}
	operator bool&() { return boolvalue; }
	operator const bool&() const { return boolvalue; }
private:
	bool boolvalue;
};
template<typename T1, typename T2> ostream& operator<<(ostream& s, pair<T1, T2>& p) {return s << "(" << p.first << ", " << p.second << ")";}
template<typename T> ostream& operator<<(ostream& s, dvector<T>& v) {
	for (int i = 0, len = v.size(); i < len; ++i){ s << v[i]; if (i < len - 1) s << "\t"; } return s; }
template<typename T> ostream& operator<<(ostream& s, dvector< dvector<T> >& vv) {
	for (int i = 0, len = vv.size(); i < len; ++i){ s << vv[i] << endl; } return s; }
template<typename T1, typename T2> ostream& operator<<(ostream& s, map<T1, T2>& m) {
	s << "{" << endl; for (auto itr = m.begin(); itr != m.end(); ++itr){ s << "\t" << (*itr).first << " : " << (*itr).second << endl; } s << "}" << endl; return s; }
template<typename T> ostream& operator<<(ostream& s, set<T>& se) {
	s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}" << endl; return s; }
template<typename T> ostream& operator<<(ostream& s, multiset<T>& se) {
	s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}" << endl; return s; }
#ifdef LOCAL_DEV
	#define debug(var) std::cout<<#var" = "<<var<<std::endl
#else
	#define debug(var)
#endif
#ifdef LOCAL_TEST
	#define vector dvector
	#define bool dbool
#endif

/*-----8<-----8<-----*/


class Edge {
public:
	ll from,to,cost;
	Edge() {}
	Edge(ll from, ll to, ll cost) : from(from), to(to), cost(cost) {}
};
ostream& operator<<(ostream& s, const Edge& e) {
	s << "{ " << e.from << " -> " << e.to << ", " << e.cost << " }";
	return s;
}

/*
引数
　g:探索するグラフ
　start:この点を根とする全域木を求める
戻り値
　return:最小全域木を構成する辺のコストの総和
　ming:最小全域木のグラフ
*/
ll prim(const vector<vector<Edge>> &g, vector<vector<Edge>> &ming, ll start = 0) {
	ll n = g.size();
	ming.assign(n, vector<Edge>());
	ll mincost = 0;
	vector<bool> visited(n,false);
	priority_queue<Edge, vector<Edge>, function<bool(Edge,Edge)>> que(
		[](const Edge &x, const Edge &y){
			return x.cost != y.cost ? (x.cost > y.cost) : 
				(x.from != y.from ? x.from < y.from : x.to < y.to);
		}
	);
	
	que.push( Edge(-1, start, 0) );
	while (!que.empty()) {
		Edge e = que.top();
		que.pop();
		if (visited[e.to]) continue;
		visited[e.to] = true;
		if (e.from>=0) ming[e.from].push_back(e);
		mincost += e.cost;
		for(Edge f:g[e.to]) {
			if (!visited[f.to]) que.push(f);
		}
	}
	return mincost;
}

class Machi{
public:
	ll x,y,index;
	Machi() {}
};

signed main() {
	ll N;
	cin>>N;
	vector<vector<Edge>> g(N,vector<Edge>());
	vector<Machi> a(N);

	rep(i,N){
		ll x,y;
		cin>>x>>y;
		Machi m;
		a[i].x=x;
		a[i].y=y;
		a[i].index=i;
	}

	sort(a.begin(), a.end(), [](const Machi &x, const Machi &y) {
		return x.x < y.x;
	});
	rep(i,N-1){
		ll cost=min(abs(a[i].x-a[i+1].x),abs(a[i].y-a[i+1].y));
		Edge e;
		e.from=a[i].index;
		e.to=a[i+1].index;
		e.cost=cost;
		g[e.from].push_back(e);
		Edge f;
		f.from=a[i+1].index;
		f.to=a[i].index;
		f.cost=cost;
		g[f.from].push_back(f);	
	}

	sort(a.begin(), a.end(), [](const Machi &x, const Machi &y) {
		return x.y < y.y;
	});
	rep(i,N-1){
		ll cost=min(abs(a[i].x-a[i+1].x),abs(a[i].y-a[i+1].y));
		Edge e;
		e.from=a[i].index;
		e.to=a[i+1].index;
		e.cost=cost;
		g[e.from].push_back(e);
		Edge f;
		f.from=a[i+1].index;
		f.to=a[i].index;
		f.cost=cost;
		g[f.from].push_back(f);		
	}

	debug(g);
	vector<vector<Edge>> ming;
	ll mincost=prim(g, ming);
	p(mincost);
	debug(ming);
	return 0;
}


Measured memory_bytes: 24820