#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
 
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <ios>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <valarray>
#include <vector>
 
#if __cplusplus >= 201103L
#include <array>
#include <forward_list>
#include <random>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <unordered_map>
#include <unordered_set>
#endif
 
#define F first
#define S second
#define MP make_pair
#define pb push_back
#define all(a) a.begin(), a.end()
#define lcm( a, b ) (a)/__gcd((a),(b))*(b)
#define endl '\n'
 
using namespace std;
 
typedef long long LL;
typedef pair< int, int > P;
typedef pair< LL, LL > LP;
typedef pair< P, int > Pi;
typedef pair< P, P > PP;
 
static const int INF = INT_MAX;
static const LL LINF = LLONG_MAX;
static const int MIN = INT_MIN;
static const LL LMIN = LLONG_MIN;
static const int MOD = 1000000007;
static const int SIZE = 100005;
 
const int dx[] = {0, -1, 1, 0};
const int dy[] = {-1, 0, 0, 1};
 
vector< int > Div( int n ) {
    vector< int > ret;
    for( int i = 1; i * i <= n; ++i ) {
        if( n % i == 0 ) {
            ret.pb( i );
 
            if( i * i != n ) ret.pb( n / i );
        }
    }
    sort( all( ret ) );
    return ret;
}
 
int Root( int x );
bool Unite( int x, int y );
LL Kruskal();
 
vector< pair< LL, P > > edge;
int root[SIZE];
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
 
    int n;
    cin >> n;
    for( int i = 0; i < SIZE; ++i ) {
        root[i] = i;
 
    }
 
    vector< LP > x_edge, y_edge;
    for( LL i = 0; i < n; ++i ) {
        LL x, y;
        cin >> x >> y;
        x_edge.pb( MP( x, i ) );
        y_edge.pb( MP( y, i ) );
 
    }
    sort( all( x_edge ) );
    sort( all( y_edge ) );
 
    for( int i = 0; i < n - 1; ++i ) {
        LL x_min_cost = abs( x_edge[i].F - x_edge[i + 1].F );
        LL y_min_cost = abs( y_edge[i].F - y_edge[i + 1].F );
 
        edge.pb( MP( x_min_cost, MP( x_edge[i].S, x_edge[i + 1].S ) ) );
        edge.pb( MP( y_min_cost, MP( y_edge[i].S, y_edge[i + 1].S ) ) );
 
    }
 
    cout << Kruskal() << endl;
 
    return 0;
}
 
int Root( int x ) {
    if( x == root[x] ) {
        return x;
 
    }
 
    return root[x] = Root( root[x] );
 
}
 
bool Unite( int x, int y ) {
    int rx, ry;
    rx = Root( x );
    ry = Root( y );
    if( rx == ry ) {
        return false;
 
    }
 
    if( rx > ry ) {
        root[ry] = rx;
 
    } else {
        root[rx] = ry;
 
    }
    return true;
 
}
 
LL Kruskal() {
    sort( all( edge ) );
 
    LL res = 0;
    for( int i = 0; i < edge.size(); ++i ) {
        if( Unite( edge[i].S.F, edge[i].S.S ) ) {
            res += edge[i].F;
 
        }
    }
 
    return res;
}


Measured memory_bytes: 10084