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

void testcase() {
    ll n, components = 0;
    cin >> n;

    map<pair<ll, bool>, vector<pair<ll, bool>>> neighbors; // true -> is column

    for(ll i = 0; i < n; ++i) {
        ll x, y;
        cin >> x >> y;
        
        neighbors[{x, false}].push_back({y, true});
        neighbors[{y, true}].push_back({x, false});
    }

    while(!neighbors.empty()){
        deque<pair<ll, bool>> q;
        set<pair<ll, bool>> v;
        v.insert(neighbors.begin()->first);
        q.push_back(neighbors.begin()->first);
        while(!q.empty()) {
            auto current = q.front();
            q.pop_front();
            // cout << current.first << " " << current.second << " " << components << "\n";

            for(auto& x: neighbors[current]) {
                if(v.find(x) != v.end()) continue;
                v.insert(x);
                q.push_back(x);
            }
            neighbors.erase(current);
        }
        components++;
    }

    cout << components - 1 << "\n";
}



int main() {
    testcase();
}