#include <bits/stdc++.h>

using namespace std;

pair<int,int> points[105];
int id[105],numOfComponents,N;

int makeSet(){
    for (int i=0;i<=100;i++){
        id[i]=i;
    }
}

int find(int i){
    if (i==id[i])return i;
    return id[i]=find(id[i]);
}

void unite(int u,int v){
    int U = find(u);
    int V = find(v);
    if (U!=V){
        id[V]=U;
        numOfComponents--;
    }
}

int main(){
    cin >> N;
    makeSet();
    for (int i=0;i<N;i++){
        cin >> points[i].first >> points[i].second;
    }
    numOfComponents=N;
    for (int i=0;i<N;i++){
        for (int j=0;j<N;j++){
            if (i==j)continue;
            if (points[i].first==points[j].first || points[i].second==points[j].second){
                unite(i,j);
            }
        }
    }
    cout << numOfComponents-1 << endl;
}