#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vll = vector<ll>;
using pi = pair<int, int>;
using vpi = vector<pi>;

struct dsu
{
    using rec = int;
    using vrec = vector<int>;

    vi par;
    int comps = 0;

    dsu(int n) : par(n), comps(n) { iota(par.begin(), par.end(), 0); }

    int find(int pos)
    {
        if (par[pos] == pos)
            return pos;
        return par[pos] = find(par[pos]);
    }

    void uni(int c, int p)
    {
        int ar = find(c);
        int br = find(p);
        if (ar != br)
        {
            --comps;
            par[ar] = br;
        }
    }
};

void solve()
{
    int n;
    cin >> n;
    vpi pts(n);
    for (auto& x : pts)
        cin >> x.first >> x.second;

    dsu ds(n);
    
    vi ord(n);
    iota(ord.begin(), ord.end(), 0);

    sort(ord.begin(), ord.end(), [&](auto a, auto b) { return pts[a].first < pts[b].first; });
    for (int i = 1; i < n; ++i)
    {
        if (pts[ord[i]].first == pts[ord[i-1]].first)
            ds.uni(ord[i], ord[i-1]);
    }
    sort(ord.begin(), ord.end(), [&](auto a, auto b) { return pts[a].second < pts[b].second; });
    for (int i = 1; i < n; ++i)
    {
        if (pts[ord[i]].second == pts[ord[i-1]].second)
            ds.uni(ord[i], ord[i-1]);
    }

    cout << ds.comps-1 << endl;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}