#include <iostream>
#include <set>
#include <utility>
#include <queue>
#include <map>
#include <unordered_set>
#include <unordered_map>

using ll = long long;

int main() {
    std::cout.tie(nullptr);
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);

    ll N;
    std::cin >> N;

    std::set<std::pair<ll,ll>> heads;
    std::unordered_map<ll, std::vector<ll>> x_to_y;
    std::unordered_map<ll, std::vector<ll>> y_to_x;
    for (ll i = 0; i < N; i += 1) {
        ll x, y;
        std::cin >> x >> y;
        x_to_y[x].push_back(y);
        y_to_x[y].push_back(x);
        heads.insert({x, y});
    }

    std::set<std::pair<ll, ll>> visited;
    ll num_components = -1;
    std::queue<std::pair<ll, ll>> queue;
    while (!heads.empty()) {
        num_components += 1;
        {
            auto first_head = *heads.begin();
            visited.insert(first_head);
            queue.push(first_head);
            heads.erase(first_head);
        }

        while (!queue.empty()) {
            auto [current_x, current_y] = queue.front();
            queue.pop();

            for (auto &neighbor_y: x_to_y[current_x]) {
                std::pair<ll, ll> neighbour = {current_x, neighbor_y};
                if (visited.count(neighbour) != 1) {
                    queue.push(neighbour);
                    visited.insert(neighbour);
                    heads.erase(neighbour);
                }
            }
            for (auto &neighbor_x: y_to_x[current_y]) {
                std::pair<ll, ll> neighbour = {neighbor_x,current_y };
                if (visited.count(neighbour) != 1) {
                    queue.push(neighbour);
                    visited.insert(neighbour);
                    heads.erase(neighbour);
                }
            }
        }
    }

    std::cout << num_components << std::endl;

    return 0;
}