#include <bits/stdc++.h>

using namespace std;
using ll = int64_t;
using ull = uint64_t;

struct P {
	int x, y;
};


vector<P> pts;
unordered_map<int, vector<int>> xtop, ytop;

void dfs(int curr, vector<bool> &seen) {
	if (seen[curr])
		return;
	seen[curr] = true;

	if (xtop.find(pts[curr].x) != xtop.end()) {
		for (int n : xtop[pts[curr].x]) {
			dfs(n, seen);
		}
		xtop.erase(pts[curr].x);
	}
	if (ytop.find(pts[curr].y) != ytop.end()) {
		for (int n : ytop[pts[curr].y]) {
			dfs(n, seen);
		}
		ytop.erase(pts[curr].y);
	}
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	// cout << setprecision(20);
	
	int n;
	cin >> n;

	pts.reserve(n);

	for (int i = 0; i < n; ++i) {
		int x,y ;
		cin >> x >> y;
		pts.push_back({x, y});
		xtop[x].push_back(i);
		ytop[y].push_back(i);
	}

	vector<bool> seen(n, false);

	int ret = -1;
	for (int i = 0; i < n; ++i) {
		if (seen[i])
			continue;
		++ret;
		dfs(i, seen);
	}

	cout << ret << endl;

	return 0;
}