#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define fcout cout << fixed << setprecision(15)
inline int bitcount(lint n){ return __builtin_popcountl(n); }
inline int highest(lint n){ return 63 - __builtin_clzl(n); }
inline void YES(bool condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
inline void Yes(bool condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
inline void assert_NO(bool condition){ if(!condition){ cout << "NO" << endl; exit(0); } }
inline void assert_No(bool condition){ if(!condition){ cout << "No" << endl; exit(0); } }
inline void assert_minus_1(bool condition){ if(!condition){ cout << -1 << endl; exit(0); } }
lint power(lint base, lint exponent, lint module){ if(exponent % 2){ return power(base, exponent - 1, module) * base % module; }else if(exponent){ lint root_ans = power(base, exponent / 2, module); return root_ans * root_ans % module; }else{ return 1; }}
struct position{ int y, x; }; position mv[4] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}}; // double euclidean(position first, position second){ return sqrt((second.x - first.x) * (second.x - first.x) + (second.y - first.y) * (second.y - first.y)); }
template<class T, class U> string to_string(pair<T, U> x){ return to_string(x.first) + "," + to_string(x.second); } string to_string(string x){ return x; }
template<class itr> void array_output(itr start, itr goal){ string ans; for(auto i = start; i != goal; i++) ans += to_string(*i) + " "; if(!ans.empty()) ans.pop_back(); cout << ans << endl; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class T> T gcd_calc(T a, T b){ if(b){ return gcd_calc(b, a % b); }else{ return a; }}
template<class T> T gcd(T a, T b){ if(a < b) swap(a, b); return gcd_calc(a, b); }
template<class T> T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct combination{ vector<lint> fact, inv; combination(int sz) : fact(sz + 1), inv(sz + 1){ fact[0] = 1; for(int i = 1; i <= sz; i++){ fact[i] = fact[i - 1] * i % mod; } inv[sz] = power(fact[sz], mod - 2, mod); for(int i = sz - 1; i >= 0; i--){ inv[i] = inv[i + 1] * (i + 1) % mod; } } lint C(int p, int q) const{ if(q < 0 || p < q) return 0; return (fact[p] * inv[q] % mod * inv[p - q] % mod); } };
template<class itr> bool next_sequence(itr first, itr last, int max_bound){ itr now = last; while(now != first){ now--; (*now)++; if((*now) == max_bound){ (*now) = 0; }else{ return true; } } return false; }
template<class T> bool chmax(T &a, const T &b){ if(a < b){ a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b){ if(b < a){ a = b; return 1; } return 0; }
inline int at(int x, int k){ return (x >> k) & 1; }
random_device rnd;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep2(i, l, n) for(int i = int(l); i < (n); i++)
#define repr(i, n) for(int i = int(n) - 1; i >= 0; i--)

struct UnionFind {
    vector< int > data;
    
    UnionFind(int sz) {
        data.assign(sz, -1);
    }
    
    bool unite(int x, int y) {
        x = find(x), y = find(y);
        if(x == y) return (false);
        if(data[x] > data[y]) swap(x, y);
        data[x] += data[y];
        data[y] = x;
        return (true);
    }
    
    int find(int k) {
        if(data[k] < 0) return (k);
        return (data[k] = find(data[k]));
    }
    
    int size(int k) {
        return (-data[find(k)]);
    }
};

int main(){
    int N;
    cin >> N;
    pair<lint, int> x[N], y[N];
    rep(i, N){
        cin >> x[i].first >> y[i].first;
        x[i].second = y[i].second = i;
    }
    sort(x, x + N);
    sort(y, y + N);
    vector<pair<lint, pair<int, int>>> roads;
    rep(i, N - 1){
        roads.push_back({x[i + 1].first - x[i].first, {x[i].second, x[i + 1].second}});
        roads.push_back({y[i + 1].first - y[i].first, {y[i].second, y[i + 1].second}});
    }
    sort(all(roads));
    UnionFind uf(N);
    lint ans = 0;
    for(auto i: roads){
        if(uf.find(i.second.first) != uf.find(i.second.second)){
            ans += i.first;
            uf.unite(i.second.first, i.second.second);
        }
    }
    cout << ans << endl;
}


Measured memory_bytes: 9456