// Slower C++ solution:
#include <bits/stdc++.h>



using namespace std;



const int N = 2e5 + 5;



struct point {

    int x, y, id;

} a[N];



bool cmp1(const point& a, const point& b) {

    if (a.x != b.x) {

        return a.x < b.x;

    }

    return a.y < b.y;

}



bool cmp2(const point& a, const point& b) {

    if (a.y != b.y) {

        return a.y < b.y;

    }

    return a.x < b.x;

}



int n;

bool visited[N];

vector<pair<long long, int> > g[N];



long long prim(int x) {

    priority_queue<pair<long long, int>, vector<pair<long long, int> >, greater<pair<long long, int> > > pq;

    long long ans = 0;

    pq.push({0, x});

    while(!pq.empty()) {

        pair<long long, int> p = pq.top();

        pq.pop();

        x = p.second;

        if (visited[x]) {

        	continue;

		}

        ans += p.first;

        visited[x] = true;

        for(int i = 0; i < g[x].size(); i++) {

            int y = g[x][i].second;

            if (!visited[y]) {

            	pq.push(g[x][i]);

            }

        }

    }

    return ans;

}



int main() {

	ios::sync_with_stdio(false);

	cin.tie(nullptr);

	cin >> n;

	for (int i = 0; i < n; i++) {

		cin >> a[i].x >> a[i].y;

		a[i].id = i + 1;

	}

	sort(a, a + n, cmp1);

	for (int i = 1; i < n; i++) {

		g[a[i].id].push_back({abs(a[i].x - a[i - 1].x), a[i - 1].id});

		g[a[i - 1].id].push_back({abs(a[i].x - a[i - 1].x), a[i].id});

	}

	sort(a, a + n, cmp2);

	for (int i = 1; i < n; i++) {

		g[a[i].id].push_back({abs(a[i].y - a[i - 1].y), a[i - 1].id});

		g[a[i - 1].id].push_back({abs(a[i].y - a[i - 1].y), a[i].id});

	}

	cout << prim(1) << '\n';

	return 0;

}


// Faster C++ solution for the same problem (measured speedup: 4.571653819515975x):
#include <bits/stdc++.h>

using namespace std;



#define ENGZ ios::sync_with_stdio(0);cin.tie(0);ios_base::sync_with_stdio(0);

#define sfi(x) scanf("%d" , &x)

#define sfi2(x, y) scanf("%d%d" , &x,&y)

#define sfl2(x, y) scanf("%I64d%I64d" , &x,&y)

#define sfl(x) scanf("%I64d" , &x)

#define sfl3(x, y, z) scanf("%I64d%I64d%I64d", &x, &y, &z)

#define sfd(x) scanf("%lf", &x)

#define sfd2(x, y) scanf("%lf", &x, &y)

#define sfs(x) scanf("%s", &x)

#define testv(x) cerr << x << ' '

#define wtf(s) freopen((s), "w", stdout)

#define rff(s) freopen((s), "r", stdin)

#define test cerr << "here"

#define fst(x) cout << fixed << setprecision(x)

#define mod 1000000007

#define pi (2 * acos(0))

typedef long double ld;

typedef long long ll;



int par[200005], rnk[200005];



int findp(int x)

{

    if (par[x] == x)

        return x;

    return par[x] = findp(par[x]);

}



bool iscon(int x, int y)

{

    if (findp(x) == findp(y))

        return true;

    return false;

}



void con(int x, int y)

{

    int px = findp(x), py = findp(y);

    if (rnk[px] > rnk[py])

        par[py] = px;

    else if (rnk[px] < rnk[py])

        par[px] = py;

    else

        par[px] = py, rnk[px]++;

}





    pair<pair<ll, ll>, int> a[100005], b[100005];

int main()

{

    ENGZ

    int n;

    ll ans = 0;

    for (int i = 0; i < 100005; i++)

        par[i] = i;

    cin >> n;

    for (int i = 0; i < n; i++)

    {

        cin >> a[i].first.first >> a[i].first.second;

        b[i].first.first = a[i].first.second;

        b[i].first.second = a[i].first.first;

        a[i].second = b[i].second = i;

    }

    sort(a, a + n);

    sort(b, b + n);

    map<ll, vector<pair<int, int>>> mp;

    for (int i = 0; i < n - 1; i++)

    {

        mp[abs(a[i].first.first - a[i + 1].first.first)].push_back({a[i].second, a[i + 1].second});

        mp[abs(b[i].first.first - b[i + 1].first.first)].push_back({b[i].second, b[i + 1].second});

    }

    for (auto it: mp)

    {

        for (auto i: it.second)

        {

            if (!iscon(i.first, i.second))

                con(i.first, i.second), ans += it.first;

        }

    }

    cout << ans;

    return 0;

}