#include <bits/stdc++.h>
using namespace std;
template <typename A, typename B>
string to_string(pair<A, B> p);
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
string to_string(const string& s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
const long long INF = 1e9 + 7;
const long long N = 3e3 + 100;
const long double EPS = 1e-12;
long long p[N];
long long get(long long v) { return (p[v] == v ? v : p[v] = get(p[v])); }
void unite(long long a, long long b) {
  a = get(a), b = get(b);
  p[b] = a;
}
void solve() {
  long long n;
  cin >> n;
  iota(p, p + N, 0);
  vector<pair<long long, long long>> a(n);
  for (auto& i : a) {
    cin >> i.first >> i.second;
  }
  for (long long i = 0; i < n; i++) {
    for (long long j = 0; j < n; j++) {
      if (a[i].first == a[j].first || a[i].second == a[j].second) {
        42;
        unite(i, j);
      }
    }
  }
  long long res = 0;
  for (long long i = 0; i < n; i++) {
    for (long long j = 0; j < n; j++) {
      if (get(i) != get(j)) {
        unite(i, j);
        res++;
      }
    }
  }
  cout << res;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  long long tests = 1;
  while (tests-- > 0) {
    solve();
  }
  return 0;
}
