#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (int i =a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define fo(i, n) rep(i, 0, n)
#define F first
#define S second
#define MP make_pair
#define PB push_back
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef vector<pair<int, int>> vpii;
typedef vector<vector<int>> vvi;
typedef vector<ll> vll;
typedef pair<ll, ll> pll;
typedef vector<pair<ll, ll>> vpll;
typedef vector<vector<ll>> vvll;

int c = 0;
vvi g;
vi vis;

void dfs(int i) {
	if (vis[i]) return;
	vis[i] = true;
	for (int x: g[i]) dfs(x);
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    int n;
    cin >> n;

    g = vvi(n);
    vis = vi(n,0);
    map<int, int> x, y;
    fo(i, n) {
	    int a, b;
	    cin >> a >> b;
	    if (x.count(a)) {
	    	g[i].PB(x[a]);
	    	g[x[a]].PB(i);
	    }
	    if (y.count(b)) {
	    	g[i].PB(y[b]);
	    	g[y[b]].PB(i);
	    }
	    x[a] = i;
	    y[b] = i;
    }

    fo(i,n) {
	    if (!vis[i]) {
		    dfs(i);
		    c++;
	    }
    }

    cout << c-1 << endl;
}