#include <bits/stdc++.h>

using namespace std;
#define int long long


int pred[201010];
int sz[201010];
int find(int v) {
    if (pred[v] == v) return v;
    return pred[v] = find(pred[v]);
}
void make(int v) {
    pred[v] = v;
    sz[v] = 1;
    return;
}
bool merge(int a, int b) {
    a = find(a);
    b = find(b);
    if (a == b) 
        return false;
    if (sz[a] < sz[b])
        swap(a, b);
    pred[b] = a;
    sz[a] += sz[b];
    return true;
}


struct Info {
    int x, y;
    int id;
};

int n;
Info t[201010];

bool hv[201010];

signed main() {
    cin.tie(0);
    ios::sync_with_stdio(0);

    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> t[i].x >> t[i].y;
        t[i].id = i;
    }

    for (int i = 1; i <= n; i++)
        make(i);
    sort(t + 1, t + 1 + n, [](Info q, Info w) {
         return q.x < w.x;
    });
    for (int i = 1; i + 1 <= n; i++) {
        if (t[i].x == t[i + 1].x) {
            merge(t[i].id, t[i + 1].id);
        }
    }

    sort(t + 1, t + 1 + n, [](Info q, Info w) {
         return q.y < w.y;
    });
    for (int i = 1; i + 1 <= n; i++) {
        if (t[i].y == t[i + 1].y) {
            merge(t[i].id, t[i + 1].id);
        }
    }

    for (int i = 1; i <= n; i++) {
        hv[find(i)] = true;
    }
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        if (hv[i])
            ans++;
    }
    cout << ans-1 << '\n';

    return 0;
}