#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() {
    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);
    }

    vector<ll> coordIndexes(n);
    for (ll i = 0; i < n; ++i) {
        coordIndexes[i] = i;
    }

    const auto cmp = [coords](ll first, ll second) {
        const coord & a = coords[first];
        const coord & b = coords[second];
        if (a.x != b.x) return a.x < b.x;
        return a.y < b.y;
    };

    const auto cmp2 = [coords](ll first, ll second) {
        const coord & a = coords[first];
        const coord & b = coords[second];
        if (a.y != b.y) return a.y < b.y;
        return a.x < b.x;
    };

    std::sort(coordIndexes.begin(), coordIndexes.end(), cmp);

    for (ll i = 1; i < n; ++i) {
        ll firstIndex = coordIndexes[i];
        ll previousIndex = coordIndexes[i-1];
        if (coords[previousIndex].x == coords[firstIndex].x) {
            coords[previousIndex].neighbors.emplace_back(firstIndex);
            coords[firstIndex].neighbors.emplace_back(previousIndex);
        }
    }

    std::sort(coordIndexes.begin(), coordIndexes.end(), cmp2);

    for (ll i = 1; i < n; ++i) {
        ll firstIndex = coordIndexes[i];
        ll previousIndex = coordIndexes[i-1];
        if (coords[previousIndex].y == coords[firstIndex].y) {
            coords[previousIndex].neighbors.emplace_back(firstIndex);
            coords[firstIndex].neighbors.emplace_back(previousIndex);
        }
    }

    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;
}