#include <bits/stdc++.h>
using namespace std;
using ll = long long;
// #define int ll
// #define endl '\n'
#define F first
#define S second
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sz(x) (int)(x).size()

struct Coord {
    int x, y, idx;
};

void tc() {
    int n; cin >> n;
    vector<Coord> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i].x >> a[i].y;
        a[i].idx = i;
    }
    map<int, vector<Coord>> same_x, same_y;
    for (auto const& coord : a) {
        same_x[coord.x].push_back(coord);
        same_y[coord.y].push_back(coord);
    }

    map<int, bool> reached_row, reached_col;
    vector<int> component(n);
    vector<bool> seen(n);
    int res = 0;
    for (int i = 0; i < n; i++) {
        if (seen[i]) continue;
        seen[i] = true;
        res++;
        queue<Coord> q;
        q.push(a[i]);
        while (sz(q)) {
            auto [x, y, idx] = q.front(); q.pop();
            if (!reached_row[y]) {
                for (auto coord : same_y[y]) {
                    if (seen[coord.idx]) continue;
                    seen[coord.idx] = true;
                    q.push(coord);
                }
            }
            if (!reached_col[x]) {
                for (auto coord : same_x[x]) {
                    if (seen[coord.idx]) continue;
                    seen[coord.idx] = true;
                    q.push(coord);
                }
            }
        }
    }
    cout << res - 1 << endl;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    tc();
}