// Problem : D - Built?
// Contest : AtCoder - AtCoder Beginner Contest 065
// URL : https://atcoder.jp/contests/abc065/tasks/arc076_b
// Memory Limit : 256 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

//look at my code
//my code is amazing
#include<bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define ll long long
#define int long long
#define mod 1000000007 //998244353
#define fast  ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define f(i,n) for(ll i=0;i<n;i++)
#define fore(i, a, b) for (ll i = (ll)(a); i <= (ll)(b); ++i)
#define nl "\n"
#define trace(x) cerr<<#x<<": "<<x<<" "<<endl
#define trace2(x, y) cerr<<#x<<": "<<x<<" | "<<#y<<": "<<y<<endl
#define trace3(x, y, z) cerr<<#x<<":" <<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<endl
#define trace4(a, b, c, d) cerr<<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<endl
#define cout1(a) cout<<a<<nl
#define cout2(a,b) cout<<a<<" "<<b<<nl
#define cout3(a,b,c) cout<<a<<" "<<b<<" "<<c<<nl
#define cout4(a,b,c,d) cout<<a<<" "<<b<<" "<<c<<" "<<d<<nl
#define vcout(v,i) cout<<v[i].fi<<" "<<v[i].se<<nl
#define x first
#define y second
#define vc vector
#define pb push_back
#define ar array
#define all(a) (a).begin(), (a).end()
#define ms(v,n,x) fill(v,v+n,x);
#define init(c,a) memset(c,a,sizeof(c))
#define pll pair<ll,ll>
#define mll map<ll,ll>
#define sll set<ll>
#define vll vector<ll>
#define vpll vector<pll>
#define maxi(a,b,c) max(a,max(b,c))
#define maxii(a,b,c,d) max(max(a,b),max(c,d))
#define mini(a,b,c) min(a,min(b,c))
#define md(a,b)  ((a%mod)*(b%mod)+mod)%mod 
#define inf 9e18
#define cases ll T;cin>>T;while(T--)
#define BLOCK 500
//const double PI = 3.141592653589793238460;
template<typename T> bool mmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool mmin(T &m, const T q) { if (m > q) {m = q; return true;} else return false; }
typedef std::complex<double> Complex;
typedef std::valarray<Complex> CArray;
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
// void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
int dx[]={0,0,1,-1};
int dy[]={1,-1,0,0};

const int N=201010;
vpll g[N];
vector<pair<pll, pll>> edges;  // (wt,id) (u,v)

int par[N], len[N];
void setup(int n)
{
    for(int i=1; i<=n; i++) par[i] = i, len[i] = 1;
}
 
int fin(int v)
{
    if(par[v]==v) return v;
    return par[v] = fin(par[v]);
}
 
bool join(int a, int b)
{
    a = fin(a); b = fin(b);
    if(a==b) return false;
    if(len[a] < len[b]) swap(a,b);
    len[a] += len[b];
    par[b] = a;
    return true;
}

ll kruskals()
{
    int cost = 0;
    vll mst;
    vector<pair<pll, pll>> ed = edges;
    sort(all(ed));
    for(auto p: ed)
    {
        int w = p.x.x, ind = p.x.y, v = p.y.x, u = p.y.y;
        if(join(v,u))
        {
            mst.pb(ind);
            g[v].pb({u,w});
            g[u].pb({v,w});
            cost += w;
        }
    }
    
    return cost;
    //print(mst);
    //cout << cost << "\n";
}


int32_t main()
{
    
	fast
	ll n;
	cin>>n;
	vc<pair<pll,ll>> a;
	
	f(i,n){
		ll u,v;
		cin>>u>>v;
		a.pb({{u,v},i+1});
	}
	
	sort(all(a),[&](pair<pll,ll> p1,pair<pll,ll> p2){
		return p1.x.x<p2.x.x;
	});
	
	ll id=0;
	for(ll i=1;i<n;i++){
		edges.pb({{abs(a[i].x.x-a[i-1].x.x),id++},{a[i].y,a[i-1].y}});	
	}
	
	sort(all(a),[&](pair<pll,ll> p1,pair<pll,ll> p2){
		return p1.x.y<p2.x.y;
	});
	
	for(ll i=1;i<n;i++){
		edges.pb({{abs(a[i].x.y-a[i-1].x.y),id++},{a[i].y,a[i-1].y}});	
	}
	
	
	
	setup(n);
	ll ans=kruskals();
	
	cout<<ans;
	
	
    

	return 0;
    
}

Measured memory_bytes: 30708