#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef long double ld;
typedef pair<ld, ld> pdd;
#define vec vector
#define For(i, a, n) for(ll i=(ll)a;i<n;i++)
#define all(x) begin(x), end(x)
#define sz(x) (ll)size(x)

template<class A, class B>
pair<A,B>operator+(const pair<A, B>&a, const pair<A,B>&b){
    return {a.first + b.first, a.second + b.second};
}
template<class A, class B>
ostream&operator<<(ostream&os, const pair<A, B>&c){
    return os<<"("<<c.first<<", "<<c.second<<")";
}
template<class A, class B, class C>
basic_ostream<A,B>&operator<<(basic_ostream<A, B>&os, const C&c){
    for(auto itr=begin(c);itr!=end(c);++itr){
        os<<(itr==begin(c)?"":" ")<<*itr;
    }
    return os;
}
template<typename...Args>
void dbg(Args&&...args){
    ((cerr<<args<<" |"),...);cerr<<endl;
}


void solve(){

    ll n;
    cin >> n;
    vector<pair<pair<ll,ll>,ll>> xy(n);
    vector<pair<pair<ll,ll>,ll>> yx(n);
    For(i,0,n){
        ll x,y;
        cin >> x >> y;
        xy[i] = {{x,y},i};
        yx[i] = {{y,x},i};
    }
    sort(xy.begin(),xy.end());
    sort(yx.begin(),yx.end());
    vector<vector<ll>> neighbors(n);
    ll last = xy[0].first.first-1;
    For(i,0,n){
        if(xy[i].first.first == last){
            neighbors[xy[i].second].push_back(xy[i-1].second);
            neighbors[xy[i-1].second].push_back(xy[i].second);
        }else{
            last = xy[i].first.first;
        }
    }
    last = yx[0].first.first-1;
    For(i,0,n){
        if(yx[i].first.first == last){
            neighbors[yx[i].second].push_back(yx[i-1].second);
            neighbors[yx[i-1].second].push_back(yx[i].second);
        }else{
            last = yx[i].first.first;
        }
    }

    ll result = -1;
    vector<bool> done(n,false);
    For(i,0,n){
        if(done[i]){
            continue;
        }

        result++;

        queue<ll> frontier;
        frontier.push(i);
        done[i] = true;
        while(!frontier.empty()){
            ll now = frontier.front();
            frontier.pop();
            
            For(child,0,neighbors[now].size()){
                if(!done[neighbors[now][child]]){
                    done[neighbors[now][child]] = true;
                    frontier.push(neighbors[now][child]);
                }
            }

            

        }
    }

    cout << result << "\n";
    
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int t = 1;
    while(t--)solve();
    return 0;
}