#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vll vector<ll>
#define vvll vector<vll>
#define vpll vector<array<ll, 3>>
#define pll array<ll, 3>
#define rep(i, n) for(ll i = 0; i < (ll)n; i++)
#define rep1(i, n) for(ll i = 1; i <= (ll)n; i++)
#define fi first
#define se second

#define debug false

struct DSU {
    vll parent, size;

    DSU(ll n){
        parent = vll(n);
        size = vll(n);

        rep(i, n) {
            make_set(i);
        }
    }

    void make_set(ll v){
        parent[v] = v;
        size[v] = 1;
    }

    void union_set(ll a, ll b){
        a = find_set(a);
        b = find_set(b);
        if(a != b){
            if (size[a] < size[b]) swap(a, b);
            parent[b] = a;
            size[a] += size[b];
        }
    }

    ll find_set(ll a){
        if(a == parent[a]) return a;
        return find_set(parent[a]);
    }
};

int main() {
//    freopen("./in.txt", "r", stdin);
//    freopen("./out.txt", "w", stdout);
//    cout << "COMMENT THIS OUT" << endl;
    cin.tie(nullptr);
    cout.tie(nullptr);
    ios_base::sync_with_stdio(false);

    ll N; cin >> N;
    vpll xy(N);
    rep(i, N){
        ll x, y; cin >> x >> y;
        xy[i][0] = x;
        xy[i][1] = y;
        xy[i][2] = i;
    }

    sort(xy.begin(), xy.end(), [](const pll& a, const pll& b){
        return a[0] < b[0];
    });

    DSU uf(N);

    rep1(i, N-1){
        const pll& a = xy[i-1];
        const pll& b = xy[i];
        if(a[0] == b[0]){
            uf.union_set(a[2], b[2]);
        }
    }

    sort(xy.begin(), xy.end(), [](const pll& a, const pll& b){
        return a[1] < b[1];
    });

    rep1(i, N-1){
        const pll& a = xy[i-1];
        const pll& b = xy[i];
        if(a[1] == b[1]){
            uf.union_set(a[2], b[2]);
        }
    }

    unordered_map<ll, ll> x;
    rep(i, N){
        ll s = uf.find_set(i);
        if(!x.count(s)){
            x[s] = 1;
        }
    }

    ll components = 0;
    rep(i, N){
        if(x.count(i)) components++;
    }

    cout << components - 1 << endl;

    return 0;
}