#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
int main()
{
    std::ios::sync_with_stdio(false);

    ll N;
    cin >> N;
    set<pll> x;
    set<pll> y;
    vector<pll> points;
    set<pll> seen;
    for (int i = 0; i < N; i++)
    {
        ll x_0, y_0;
        cin >> x_0 >> y_0;
        pll point = pair(x_0, y_0);
        pll r_point = pair(y_0, x_0);
        points.push_back(point);
        x.insert(point);
        y.insert(r_point);
    }

    ll count = 0;
    for (int i = 0; i < N; i++)
    {
        pll point = points[i];
        if (seen.find(point) == seen.end())
        {
            count++;
            deque<pll> q;
            q.push_back(point);
            while(!q.empty())
            {
                pll p = q.front();
                q.pop_front();

                if (seen.find(p) != seen.end())
                {
                    continue;
                }
                seen.insert(p);

                pll r_p = pair(p.second, p.first);



                pll c = *(++x.find(p));
                pll d = *(--x.find(p));
                if (c.first == p.first)
                    q.push_back(*(++x.find(p)));

                if (d.first == p.first)
                    q.push_back(*(--x.find(p)));

                
                pll a = *(++y.find(r_p));
                pll b = *(--y.find(r_p));

                if (a.first == p.second)
                    q.push_back(pair(a.second, a.first));

                if (b.first == p.second)
                    q.push_back(pair(b.second, b.first));
            }
        }
    }

    std::cout << count - 1 << endl;

    return 0;
}