#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pi;
typedef vector<ll> vi;

#define sz(x) ((ll)(x).size())
#define all(x) begin(x), end(x)
#define rep(i, a, b)  for(int i = a; i < (b); ++i)

struct Boar {
    int x, y;

    bool operator<(const Boar &rhs) const {
        return std::tie(x, y) < std::tie(rhs.x, rhs.y);
    }

    bool operator>(const Boar &rhs) const {
        return rhs < *this;
    }

    bool operator<=(const Boar &rhs) const {
        return !(rhs < *this);
    }

    bool operator>=(const Boar &rhs) const {
        return !(*this < rhs);
    }

    bool operator==(const Boar &rhs) const {
        return std::tie(x, y) == std::tie(rhs.x, rhs.y);
    }

    bool operator!=(const Boar &rhs) const {
        return !(rhs == *this);
    }
};

#define SUCCESSFUL 1

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    cin.exceptions(ios::failbit);

    int n;
    cin >> n;

    vector<Boar> boars;
    boars.reserve(n);

    set<ll> non_visited;
    map<ll, vector<ll>> by_x;
    map<ll, vector<ll>> by_y;
    for (int i = 0; i < n; ++i) {
        boars.emplace_back();
        cin >> boars.back().x >> boars.back().y;

        by_x[boars.back().x].emplace_back(i);
        by_y[boars.back().y].emplace_back(i);

        non_visited.emplace(i);
    }

    ll components_cnt = 0;
    while (!non_visited.empty()) {
        components_cnt += 1;

        ll start = *non_visited.begin();
        non_visited.erase(non_visited.begin());
        vector<ll> to_visit{start};

        while (!to_visit.empty()) {
            ll current = to_visit.back();
            to_visit.pop_back();

            vi& neighbours_x = by_x.at(boars.at(current).x);
            vi& neighbours_y = by_y.at(boars.at(current).y);

            for (ll neighbour : neighbours_x) {
                if (non_visited.erase(neighbour) != SUCCESSFUL) {
                    continue;
                }
                to_visit.emplace_back(neighbour);
            }
            for (ll neighbour : neighbours_y) {
                if (non_visited.erase(neighbour) != SUCCESSFUL) {
                    continue;
                }
                to_visit.emplace_back(neighbour);
            }
        }
    }

    cout << components_cnt - 1 << '\n';
}