#include <bits/stdc++.h>
using namespace std;

template <class T>
ostream& operator<<(ostream& out, const vector<T> &cont) {
    out << "[";
    for(const auto &x: cont) out << x<< ", ";
    out << "]";
    return out;
}

#define dmp(x) cerr << #x << " = " << x << endl
#define dmpn(x) cerr << #x << " = " << x <<"; "

#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define sz(x) (int) (x).size()
#define int long long

typedef long long ll;
typedef pair<int, int> pii;
typedef long double ld;

int components = 0;
set<pii> visited;
vector<pair<int, int>> points;
map<int, vector<int>> row, col;
void dfs(pii i){
    if(visited.find(i) != visited.end())
        return;

    visited.insert(i);
    for(int x:row[i.second]){
        dfs({x, i.second});
    }
    for(int y:col[i.first]){
        dfs({i.first, y});
    }
}


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

        row[y].push_back(x); 
        col[x].push_back(y);   
        points.push_back({x,y});
    }


    for(auto &i:points){
        if(visited.find(i) == visited.end()){
            components++;
            dfs(i);
        }
    }

    cout << components-1 << '\n';


    
}

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    solve();
    return 0;
}