#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()
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;

class UF{
public:
    int n;
    vector<int> par;
    UF(int n_){
        n=n_;
        par.assign(n, 0);
        iota(all(par),0);
    }
    int root(int a){
        vector<int> were;
        while (a!=par[a]){
            were.push_back(a);
            a=par[a];
        }
        for (int i:were){
            par[i]=a;
        }
        return a;
    }

    bool union_(int a, int b){
        int pa=root(a);
        int pb=root(b);

        if (pa!=pb){
            par[pa] = pb;
            return 1;
        }

        return 0;
    }
};

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

    map<int,vi> rows;
    map<int,vi> cols;

    for (int i=0;i<n;i++){
        int x,y;
        cin>>x>>y;

        if (rows.count(y)==0){
            rows[y]={};
        }
        rows[y].push_back(i);

        if (cols.count(x)==0){
            cols[x]={};
        }
        cols[x].push_back(i);
    }
    vector<pii>E;

    for (auto [c, vec]: cols){
        for (int i=1;i<vec.size();i++){
            E.push_back({vec[i-1],vec[i]});
        }
    }
    for (auto [c, vec]: rows){
        for (int i=1;i<vec.size();i++){
            E.push_back({vec[i-1],vec[i]});
        }
    }

    UF uf(n);
    int cons=n-1;
    for (auto[i,j]:E){
        if (uf.union_(i,j)){
            cons--;
        }
    }

    cout<<cons<<'\n';


}