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

class UnionFind {
private:
    vector<int> rank, p;
    int sz;
public:
    UnionFind(int n) {
        rank.assign(n, 0);
        p.assign(n, 0);
        for (int i = 0; i < n; i++) p[i] = i;
        sz = n;
    }

    int find(int a) {
        if (p[a] == a) return a;
        return p[a] = find(p[a]);
    }

    int getNum() {
        return sz;
    }

    void unite(int a, int b) {
        int pa = find(a);
        int pb = find(b);

        if (pa == pb) return;

        if (rank[pa] == rank[pb]) {
            rank[pa]++;
            p[pb] = pa;
        } else if (rank[pa] > rank[pb]) {
            p[pb] = pa;

        }else {
            p[pa] = pb;

        }
        sz--;
    }
};

int main() {

    int n;
    scanf("%d", &n);

    unordered_map<int, int> xs;
    unordered_map<int, int> ys; 
    vector<pair<int, int>> pts(n);
    UnionFind uf(n);

    for (int i = 0; i < n; i++) {
        int a, b;
        scanf("%d %d", &a, &b);
        pts[i] = {a, b};
        if (xs.find(a) != xs.end()) {
            uf.unite(xs[a], i);
        } else {
            xs[a] = i;
        }
        if (ys.find(b) != ys.end()) {
            uf.unite(ys[b], i);
        } else {
            ys[b] = i;
        }
    }



    printf("%d\n", uf.getNum() - 1);


    return 0;
}