#include <bits/stdc++.h>
#define ll long long
#define pb push_back
using namespace std;

vector <ll> pai;

ll find(ll x){
    if(x==pai[x]) return x;
    return pai[x] = find(pai[x]);
}

void join(ll x, ll y){
    x = find(x);
    y = find(y);
    pai[y] = x;
}

int main(){
    ll n;
    scanf("%lld", &n);
    pai.resize(n);
    for(int i=0;i<n;i++) pai[i] = i;
    ll cont=0;
    map <ll, ll> appeared;

    vector<pair<ll, ll>> entrada;
    ll nx = n;
    while(nx--){
        ll x, y;
        scanf("%lld %lld", &x, &y);
        entrada.pb({x,y});
    }

    for(int i=0;i<entrada.size();i++){
        for(int j=i+1;j<entrada.size();j++){
            if(entrada[i].first==entrada[j].first || entrada[i].second==entrada[j].second){
                join(i, j);
            }
        }
    }
    for(int i=0;i<n;i++){
        //cout << find(i) << " ";
        if(appeared.count(find(i))==0){
            appeared[find(i)] = 1;
            cont++;
        }
    }
    //cout << endl;
    printf("%lld\n", cont-1);
}