#include <iostream>
#include <vector>
#include <map>
#include <queue>
#include <set>

struct Point {
    size_t x;
    size_t y;

    friend bool operator <(const Point&a, const Point&b) {
        if (a.x == b.x) return a.y < b.y;
        
        return a.x < b.x;
    }
};

int main() {
    size_t num = 0;

    std::cin >> num;

    std::set<Point> nodes;
    std::map<size_t, std::vector<Point>> xneigh;
    std::map<size_t, std::vector<Point>> yneigh;

    for (size_t i = 0; i < num; i++) {
        Point p;
        std::cin >> p.x >> p.y;
        nodes.insert(p);
        xneigh[p.x].push_back(p);
        yneigh[p.y].push_back(p);
    }

    std::queue<Point> to_visit;
    Point first = *nodes.begin();
    to_visit.push(first);
    nodes.erase(first);
    size_t total_count = 0;

    while (!to_visit.empty()) {
        Point node = to_visit.front();
        to_visit.pop();

        for (const auto &neigh : xneigh[node.x]) {
            if (neigh.y != node.y && nodes.count(neigh)) {
                to_visit.push(neigh);
            }
            nodes.erase(neigh);
        }

        for (const auto &neigh : yneigh[node.y]) {
            if (neigh.x != node.x && nodes.count(neigh)) {
                to_visit.push(neigh);
            }
            nodes.erase(neigh);
        }

        if (to_visit.empty() && !nodes.empty()) {
            total_count += 1;
            to_visit.push(*nodes.begin());
        }
    }

    std::cout << total_count << std::endl;
}