#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...); }

class UnionFind {
private:
	vector<int> par, height, size;
public:
	UnionFind(int n) {
		par.resize(n);
		REP(i, n) {
			par[i] = i;
		}
		height.resize(n, 0);
		size.resize(n, 1);
	}
	int root(int x) {
		if (par[x] == x) {
			return x;
		} else {
			par[x] = root(par[x]);
			return par[x];
		}
	}
	bool same(int x, int y) {
		return root(x) == root(y);
	}
	void unite(int x, int y) {
		x = root(x);
		y = root(y);
		if (x == y)return;
		if (height[x] < height[y]) {
			par[x] = y;
			size[y] += size[x];
		} else {
			par[y] = x;
			size[x] += size[y];
			if (height[x] == height[y])height[x]++;
		}
	}
	int cnt(int x) {
		x = root(x);
		return size[x];
	}
};

template<typename T>
class MinimumSpanningTree {
private:
	vector<int> from, to;
	vector<pair<T, int>> cost;
	int n,m;
public:
	MinimumSpanningTree<T>(vector<int>& from, vector<int>& to, vector<T>& cost,int n) :from(from), to(to), n(n) {
		this->m = (int)cost.size();
		this->cost.resize(m);
		for (int i = 0; i < m; ++i) {
			this->cost[i].first = cost[i];
			this->cost[i].second = i;
		}
		sort(this->cost.begin(), this->cost.end());
	}
	vector<int> Kruskal() {
		vector<int> res; //mstを構成するindexの集合
		UnionFind uf(n);
		for (int i = 0; i < m; ++i) {
			int index = this->cost[i].second;
			if (!uf.same(from[index], to[index])) {
				res.push_back(index);
				uf.unite(from[index], to[index]);
			}
			if (res.size() == n - 1) {
				break;
			}
 		}
		return res;
	}
};

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));
	vector<int> from, to;
	vector<ll> cost;
	REP(i, n - 1) {
		from.push_back(px[i].second);
		to.push_back(px[i + 1].second);
		cost.push_back(abs(px[i].first - px[i + 1].first));
		from.push_back(py[i].second);
		to.push_back(py[i + 1].second);
		cost.push_back(abs(py[i].first - py[i + 1].first));
	}
	MinimumSpanningTree<ll> mst(from, to, cost, n);
	vector<int> edges = mst.Kruskal();
	ll res = 0;
	REP(i, edges.size()) {
  		res += cost[edges[i]];
	}
	put(res);
	return 0;
}


Measured memory_bytes: 14812