#include <bits/stdc++.h>

using namespace std;


void addEdges(vector<vector<int>> & g, const vector<pair<int, int>> & v) {
    int i = 0, j = 0;
    while(j < v.size()-1) {
        j++;
        if(v[i].first == v[j].first) {
            g[v[i].second].push_back(v[j].second);
            g[v[j].second].push_back(v[i].second);
        } else {
            i=j;
        }

    }
}



int main() {
    int N;
    cin >> N;
    vector<pair<int, int>> y(N), x(N);
    for(int i = 0; i < N; i++) {
        x[i].second = i;
        y[i].second = i;
        cin >> x[i].first >> y[i].first;
    }

    vector<vector<int>> g(N);
    sort(x.begin(), x.end());
    sort(y.begin(), y.end());
    addEdges(g,x);
    addEdges(g,y);



    vector<bool> seen(N, false);
    int result = 0;
    queue<int> q;
    for(int i = 0; i < N; i++) {
        if(!seen[i]) {
            result++;
            seen[i] = true;
            q.push(i);
            while(!q.empty()) {
                for(auto a : g[q.front()]) {
                    if(!seen[a]) {
                        seen[a] = true;
                        q.push(a);
                    }
                }
                q.pop();
            }

        }
    }
    cout << result -1 << '\n';


}