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

template<typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << '[';
    for(int i = 0; i < v.size(); i++)
    {
        if(i)
            os << ", ";
        os << v[i];
    }
    os << ']';
    return os;
}

void solve()
{
    int n;
    cin >> n;
    map<int, vector<int>> x2ys; // mapa x => vektor y souradnic bodu v tom xu
    map<int, vector<int>> y2xs;
    for(int i = 0; i < n; i++)
    {
        int x, y;
        cin >> x >> y;
        x2ys[x].push_back(y);
        y2xs[y].push_back(x);
    }

    // for(auto& [key, _] : x2ys)
    //     cout << key << ": " << x2ys[key] << endl;
    // cout << endl;
    // for(auto& [key, _] : y2xs)
    //     cout << key << ": " << y2xs[key] << endl;
    // y2xs.erase(3);
    // cout << endl;
    // for(auto& [key, _] : y2xs)
    //     cout << key << ": " << y2xs[key] << endl;

    int noc = 0; // num of ocmponents
    while(!x2ys.empty() || !y2xs.empty())
    {
        noc++;

        vector<int> x_todo;
        vector<int> y_todo;
        if(!x2ys.empty())
        {
            auto it = x2ys.begin();
            for(int y : it->second)
                y_todo.push_back(y);
            x2ys.erase(it->first);

        }
        else if(!y2xs.empty())
        {
            auto it = y2xs.begin();
            for(int x : it->second)
                x_todo.push_back(x);
            y2xs.erase(it->first);
        }

        while(!x_todo.empty() || !y_todo.empty())
        {
            for(int x : x_todo)
            {
                auto it = x2ys.find(x);
                if(it == x2ys.end())
                    continue;
                for(int y : it->second)
                    y_todo.push_back(y);
                x2ys.erase(it);
            }
            x_todo = {};
            for(int y : y_todo)
            {
                auto it = y2xs.find(y);
                if(it == y2xs.end())
                    continue;
                for(int x : it->second)
                    x_todo.push_back(x);
                y2xs.erase(it);
            }
            y_todo = {};
            // cout << "x_todo: " << x_todo << endl;
            // cout << "y_todo: " << y_todo << endl;
            // cout << endl;
        }

        //yka = x2ys.
    }

    // cout << "noc: " << noc << endl;
    cout << (noc - 1) << endl;
}

int32_t main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    solve();

    return 0;
}