#include<bits/stdc++.h>
using namespace std;

// Shortcut

#define int long long
#define endl '\n'
#define eb emplace_back
#define pb push_back
#define pob pop_back
#define mp make_pair
#define upb upper_bound
#define lwb lower_bound
#define fi first
#define se second
#define For(i, l, r) for (int i = l; i < r; i++)
#define ForE(i, l, r) for (int i = l; i <= r; i++)
#define Ford(i, r, l) for (int i = r; i > l; i--)
#define FordE(i, r, l) for (int i = r; i >= l; i--)
#define Fora(i, a) for (auto i : a)

// I/O & Debug

#define PrintV(a) for (int iiii = 0; iiii < a.size(); iiii++) cout << a[iiii] << ' ';
#define PrintVl(a) for (int iiii = 0; iiii < a.size(); iiii++) cout << a[iiii] << endl;
#define PrintA(a, n) for (int iiii = 0; iiii < n; iiii++) cout << a[iiii] << ' ';
#define PrintAl(a, n) for (int iiii = 0; iiii < n; iiii++) cout << a[iiii] << endl;
#define Ptest(x) return cout << x, 0;
#define gl(s) getline(cin, s);
#define setpre(x) fixed << setprecision(x)
/*
#define debug(args...){ string _sDEB = #args; replace(_sDEB.begin(), _sDEB.end(), ',', ' '); stringstream _ssDEB(_sDEB); istream_iterator<string> _itDEB(_ssDEB); DEB(_itDEB, args); }
void DEB(istream_iterator<string> it) {}
template<typename T, typename... Args>
void DEB(istream_iterator<string> it, T a, Args... args){
    cout << *it << " = " << a << endl;
    DEB(++it, args...);
}
*/

// Functions

//#define isvowel(a) (a == 'a' || a == 'e' || a == 'i' || a == 'o' || a == 'u')
#define bend(a) a.begin(), a.end()
#define rbend(a) a.rbegin(), a.rend()
#define mset(a) memset(a, 0, sizeof(a));
//mt19937 rando(chrono::steady_clock::now().time_since_epoch().count());

// Data Structure

#define pque priority_queue
#define mts multiset
typedef long long ll;
typedef long double ld;
typedef vector <int> vi;
typedef vector <ll> vll;
typedef vector <ld> vld;
typedef vector <string> vs;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef vector <vi > vvi;
typedef vector <vll > vvll;
typedef vector <pii > vpii;
typedef vector <pll > vpll;

const int N = 1e5 + 5, mod = 1e9 + 7, inf = 1e18 + 5;

int n;

struct node{
    int u, v, w;
    bool operator< (const node &a) const{
        return w < a.w;
    }
} e[N * 2];

struct point{
    int w, id;
    bool operator< (const point &a) const{
        return w < a.w;
    }
} x[N], y[N];

int par[N];

int get(int x){
    while (x != par[x]){
        x = par[x] = par[par[x]];
    }
    return x;
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    cin >> n;
    ForE(i, 1, n){
        cin >> x[i].w >> y[i].w;
        x[i].id = i;
        y[i].id = i;
        par[i] = i;
    }
    sort(x + 1, x + n + 1);
    sort(y + 1, y + n + 1);
    int sz = 0, sum = 0, cnt = 1;
    For(i, 1, n){
        e[++sz] = (node){x[i].id, x[i + 1].id, abs(x[i].w - x[i + 1].w)};
    }
    For(i, 1, n){
        e[++sz] = (node){y[i].id, y[i + 1].id, abs(y[i].w - y[i + 1].w)};
    }
    sort(e + 1, e + sz + 1);
    ForE(i, 1, sz){
        int pu = get(e[i].u), pv = get(e[i].v);
        if (pu == pv){
            continue;
        }
        sum += e[i].w;
        par[pu] = pv;
        if (++cnt == n){
            break;
        }
    }
    cout << sum;
}

/*
==================================+
INPUT:                            |
------------------------------    |

------------------------------    |
==================================+
OUTPUT:                           |
------------------------------    |

------------------------------    |
==================================+
*/

Measured memory_bytes: 8832