//file_name:ABC65_D.cpp
#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define rng(a) a.begin(),a.end()
#define maxs(x,y) (x = max(x,y))
#define mins(x,y) (x = min(x,y))
#define limit(x,l,r) max(l,min(x,r))
#define lims(x,l,r) (x = max(l,min(x,r)))
#define isin(x,l,r) ((l) <= (x) && (x) < (r))
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcountll
#define uni(x) x.erase(unique(rng(x)),x.end())
#define snuke srand((unsigned)clock()+(unsigned)time(NULL));
#define show(x) cout<<#x<<" = "<<x<<endl;
#define PQ(T) priority_queue<T,v(T),greater<T> >
#define bn(x) ((1<<x)-1)
#define dup(x,y) (((x)+(y)-1)/(y))
#define newline puts("")
#define v(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
typedef long long int ll;
typedef unsigned uint;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
inline int in() { int x; scanf("%d",&x); return x;}
template<typename T>inline istream& operator>>(istream&i,v(T)&v)
{rep(j,sz(v))i>>v[j];return i;}
template<typename T>string join(const v(T)&v)
{stringstream s;rep(i,sz(v))s<<' '<<v[i];return s.str().substr(1);}
template<typename T>inline ostream& operator<<(ostream&o,const v(T)&v)
{if(sz(v))o<<join(v);return o;}
template<typename T1,typename T2>inline istream& operator>>(istream&i,pair<T1,T2>&v)
{return i>>v.fi>>v.se;}
template<typename T1,typename T2>inline ostream& operator<<(ostream&o,const pair<T1,T2>&v)
{return o<<v.fi<<","<<v.se;}
template<typename T>inline ll suma(const v(T)& a) { ll res(0); for (auto&& x : a) res += x; return res;}
const double eps = 1e-10;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#define dame { puts("-1"); return 0;}
#define yn {puts("Yes");}else{puts("No");}
const int MX = 200005;

    struct edge{
        int u,v,cost;
    };


    // int scan
    /*
    int x;
    scanf("%d",&x);
    int y;
    scanf("%d",&y);
    int z;
    scanf("%d",&z);

    // matrix scan
    /*
    ll a[n] = {};
    rep(i,n){
        scanf("%lld",&a[i]);
    }
    */

    // string scan
    /*
    string s;
    cin >> s;
    */





// Union-Find
// n要素で初期化
void init(int par[], int rank[], int n){
    for(int i=0;i<n;i++){
        par[i] = i;
        rank[i] = 0;
    }
}

// 木の根を求める
int find(int par[], int x){
    if(par[x] == x){
        return x;
    }else{
        return par[x] = find(par,par[x]);
    }
}

// xとyの属する集合を併合
void unite(int par[], int rank[], int x, int y){
    x = find(par,x);
    y = find(par,y);
    if(x == y) return;

    if(rank[x] < rank[y]){
        par[x] = y;
    }else{
        par[y] = x;
        if(rank[x] == rank[y]) rank[x]++;
    }
}

// xとyが同じ集合に属するか否か
bool same(int par[], int x, int y){
    return find(par,x) == find(par,y);
}

bool comp(const edge& e1, const edge& e2){
    return e1.cost < e2.cost;
}

long long int kruscal(int V, int E, edge es[]){
    sort(es, es + E, comp); // edge.costが小さい順にソートする

    int par[V]; // 親
    int rank[V]; // 木の深さ
    init(par, rank, V); // Union-Findの初期化
    long long int res = 0;
    for(int i=0; i<E; i++){
        edge e = es[i];
        if(!same(par,e.u, e.v)){
            unite(par, rank, e.u, e.v);
            res += e.cost;
        }
    }
    return res;
}

int cmp1(const void *a, const void *b){ // 昇順
    // qsort
    // http://www.cc.kyoto-su.ac.jp/~yamada/ap/qsort.html

    return *(int*)a - *(int*)b;
}
int cmp2(const void *a, const void *b){ // 降順
    // qsort
    // http://www.cc.kyoto-su.ac.jp/~yamada/ap/qsort.html

    return *(int*)b - *(int*)a;
}

int main() {
    // main関数で定義するもの



    int n;
    scanf("%d",&n);

    int V = n; // 頂点数
    int E = (n-1)*2; // 辺数
    edge es[E]; // 辺の大きさ

    int a[n][3];
    rep(i,n){
        scanf("%lld%lld",&a[i][0],&a[i][1]);
        a[i][2] = i;
    }

    int count = 0; // 辺の数
    // x座標
    qsort(a, n, sizeof(a[0]), cmp1); // 1列目で昇順ソート
    rep(i,n-1){
        es[count].u = a[i][2];
        es[count].v = a[i+1][2];
        es[count].cost = a[i+1][0] - a[i][0];
        count++;
    }

    // y座標
    rep(i,n){
        swap(a[i][0],a[i][1]);
    }
    qsort(a, n, sizeof(a[0]), cmp1); // 1列目で昇順ソート
    rep(i,n-1){
        es[count].u = a[i][2];
        es[count].v = a[i+1][2];
        es[count].cost = a[i+1][0] - a[i][0];
        count++;
    }

    ll ans = 0;
    ans = kruscal(V,E,es);

    cout << ans << endl;
    return 0;
}



Measured memory_bytes: 5864