#include <bits/stdc++.h>

#define int long long
#define vec vector
#define forn(i, n) for(int i = 0;i<n;i++)
#define fi first
#define se second
#define all(a) (a).begin(), (a).end()
#define read(a) forn(i, (a).size()) cin>>(a)[i]
#define write(a) forn(i, (a).size()) cout<<(a)[i] << " "; cout << "\n";



using namespace std;

typedef pair<int, int> pii;

int mod = 1e9+7;
vec<bool> used;
vec<vec<int> > g;

void dfs(int v){
    if(used[v])
        return;
    used[v] = true;
    for(int u: g[v])
        dfs(u);
}

struct st{
    int x, y, num;
};

bool comp1(st a, st b){
    return a.x < b.x;
}

bool comp2(st a, st b){
    return a.y < b.y;
}

void solve(){
    int n;
    cin>>n;

    vec<st> points(n);
    for(int i = 0; i<n;i++) {
        cin >> points[i].x >> points[i].y;
        points[i].num = i;
    }

    g.resize(n);
    sort(all(points), comp1);

    for(int i = 0;i<n;){
        int j = i+1;
        int from = points[i].num;
        while(points[j].x == points[i].x){
            int to = points[j].num;
            g[from].push_back(to);
            g[to].push_back(from);
            j++;
        }
        i = j;
    }

    sort(all(points), comp2);
    for(int i = 0;i<n;){
        int j = i+1;
        int from = points[i].num;
        while(points[j].y == points[i].y){
            int to = points[j].num;
            g[from].push_back(to);
            g[to].push_back(from);
            j++;
        }
        i = j;
    }


    used.assign(n,false);
    int ans = -1;
    for(int i=0;i<n;i++){
        if(!used[i]){
            ans++;
            dfs(i);
        }
    }
    cout<<ans<<'\n';
}

signed main()
{
    int tt = 1;
    while(tt--){
        solve();
    }
}