#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;

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);
}

void solve(){
    int n;
    cin>>n;
    map<int,int> tr;
    int ind = 0;

    for(int i=0;i<n;i++){
        int x,y;
        cin>>x>>y;
        if(tr.find(x)==tr.end()){
            tr[x] = ind;
            ind++;
        }
        if(tr.find(y)==tr.end()){
            tr[y] = ind;
            ind++;
        }
        while(g.size()<ind){
            g.push_back({});
        }
        g[tr[x]].push_back(tr[y]);
        g[tr[y]].push_back(tr[x]);
    }
    used.assign(ind,false);
    int ans = -1;
    for(int i=0;i<ind;i++){
        if(!used[i]){
            ans++;
            dfs(i);
        }
    }
    cout<<ans<<'\n';
}

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