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

#define int long long

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x),end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<pair<int, int>> vpii;

template<class T> using vec = vector<T>;
template<class T> using uset = unordered_set<T>;
template<class K, class V> using umap = unordered_map<K, V>;

void solve() {
    int n; cin >> n;

    vpii points(n);
    umap<int, vi> xs;
    umap<int, vi> ys;
    rep(i, 0, n) {
        int x, y; cin >> x >> y;
        points[i] = {x, y};
        xs[x].emplace_back(i);
        ys[y].emplace_back(i);
    }

    vi comp(n, -1);
    int cx = 0;
    uset<int> X, Y;
    rep(i, 0, sz(points)) {
        if (comp[i] != -1) continue;
        queue<int> q{{i}};
        while(!q.empty()) {
            int u = q.front();
            q.pop();
            comp[u] = cx;
            auto [x, y] = points[u];

            if (!X.count(x)) {
                X.emplace(x);
                for (int i: xs[x]) {
                    if (comp[i] != -1) continue;
                    q.emplace(i);
                    comp[i] = cx;
                }
            }

            if (!Y.count(y)) {
                Y.emplace(y);
                for (int i: ys[y]) {
                    if (comp[i] != -1) continue;
                    q.emplace(i);
                    comp[i] = cx;
                }
            }
        }

        cx++;
    }

    cout << cx - 1 << endl;
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    ll T = 1;
    // cin >> T;
    rep(i, 0, T) solve();
}