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

struct coord {
    ll x = 0, y = 0;
    vector<ll> neighbors;
    coord() = default;
    coord(ll x, ll y) : x(x), y(y), neighbors() {}
};

int main() {
    std::istream::sync_with_stdio(false);
    ll n;
    cin >> n;
    vector<coord> coords(n);
    for (ll i = 0; i < n; ++i) {
        ll x, y;
        cin >> x >> y;
        coords[i] = coord(x, y);
    }

    unordered_map<ll, vector<ll>> rows;
    unordered_map<ll, vector<ll>> columns;

    for (ll i = 0; i < n; ++i) {
        coord & currCoord = coords[i];
        if (rows.count(currCoord.y) == 0) rows[currCoord.y] = {i};
        else {
            ll lastCoordIndex = rows[currCoord.y][rows[currCoord.y].size() - 1];
            coord & lastCoord = coords[lastCoordIndex];
            lastCoord.neighbors.push_back(i);
            currCoord.neighbors.push_back(lastCoordIndex);
        }
    }

    for (ll i = 0; i < n; ++i) {
        coord & currCoord = coords[i];
        if (columns.count(currCoord.x) == 0) columns[currCoord.x] = {i};
        else {
            ll lastCoordIndex = columns[currCoord.x][columns[currCoord.x].size() - 1];
            coord & lastCoord = coords[lastCoordIndex];
            lastCoord.neighbors.push_back(i);
            currCoord.neighbors.push_back(lastCoordIndex);
        }
    }

    vector<bool> visited(n, false);
    ll result = 0;
    for (ll i = 0; i < n; ++i) {
        if (visited[i]) continue;
        ++result;
        queue<ll> q;
        q.push(i);
        visited[i] = true;
        while (!q.empty()) {
            ll currIndex = q.front();
            q.pop();
            const coord & currCoord = coords[currIndex];
            for (ll x : currCoord.neighbors) {
                if (visited[x]) continue;
                q.push(x);
                visited[x] = true;
            }
        }
    }
    cout << result - 1 << '\n';
    return 0;
}