#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

template <class S>
struct value_compression : vector<S> {
  bool built = false;
  using VS = vector<S>;
  using VS::VS;
  value_compression(vector<S> v) : vector<S>(move(v)) {}
  void build() {
    sort(this->begin(), this->end());
    this->erase(unique(this->begin(), this->end()), this->end());
    built = true;
  }
  template <class T>
  void convert(T first, T last) {
    assert(built);
    for (; first != last; ++first) *first = (*this)(*first);
  }
  int operator()(S x) {
    assert(built);
    return lower_bound(this->begin(), this->end(), x) - this->begin();
  }
  void clear() {
    this->clear();
    built = false;
  }
};

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  ll m;
  cin >> n >> m;
  VL x(n), y(n);
  value_compression<ll> vc;
  rep(i, n) cin >> x[i] >> y[i], vc.emplace_back(x[i]), vc.emplace_back(y[i]);
  vc.build();
  m = n;
  n = vc.size();
  // int n, m;
  // cin >> n >> m;
  set<P> es;
  vector<char> alive(n, true);
  int ans = 0;
  rep(i, m) {
    int u = vc(x[i]), v = vc(y[i]);
    if (u > v) swap(u, v);
    if (u == v) {
      ans += alive[u];
      alive[u] = false;
    } else if (es.count({u, v})) {
      es.erase({u, v});
      ans += alive[u] + alive[v];
      alive[u] = alive[v] = false;
    } else {
      es.emplace(u, v);
    }
  }
  VVI to(n);
  for (auto [u, v] : es) {
    if (alive[u] && alive[v]) {
      to[u].emplace_back(v);
      to[v].emplace_back(u);
    } else if (alive[u] || alive[v]) {
      if (alive[v]) swap(u, v);
      auto dfs = [&](auto&& self, int u) -> void {
        if (!alive[u]) return;
        ans++;
        alive[u] = false;
        for (int v : to[u]) self(self, v);
      };
      dfs(dfs, u);
    }
  }
  dsu uf(n);
  VI ecnt(n);
  rep(u, n) if (alive[u]) for (int v : to[u]) if (u < v && alive[v]) {
    int lu = uf.leader(u), lv = uf.leader(v);
    if (lu == lv) ecnt[lu]++;
    else ecnt[uf.merge(lu, lv)] = ecnt[lu] + ecnt[lv] + 1;
  }
  rep(i, n) if (uf.leader(i) == i) ans += min(ecnt[i], uf.size(i));
  cout << ans << '\n';
}