#include <algorithm>
#include <bit>
#include <bitset>
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <deque>
#include <iostream>
#include <map>
#include <random>
#include <unordered_set>
#include <unordered_map>
#include <vector>
#include <set>
#include <string>

using namespace::std;

template<typename T, typename U>
ostream& operator<< (ostream& o, const pair<T, U>& p) {
  o << "<" << p.first << ", " << p.second << ">";
  return o;
}

template <typename T>
ostream& operator<< (ostream& o, const vector<T>& v) {
 for (const auto& x : v) o << x << " ";
 return o;
}

template <typename T>
ostream& operator<< (ostream& o, const set<T>& v) {
 for (const auto& x : v) o << x << " ";
 return o;
}

template <typename T>
ostream& operator<< (ostream& o, const deque<T>& v) {
 for (const auto& x : v) o << x << " ";
 return o;
}

template <typename K, typename V>
ostream& operator<<(ostream& o, const unordered_map<K, V>& m) {
  o << "{";
  for (const auto& [k, v] : m)
    o << " " << k << ": " << v << ",";
  o << "}";
  return o;
}

template <typename T>
ostream& operator<< (ostream& o, const vector<vector<T>>& v) {
 for (const auto& x : v) o << x << endl;
 return o;
}

ostream& operator<< (ostream& o, const vector<string>& v) {
 for (const auto& x : v) o << x << endl;
 return o;
}



template <typename T>
istream& operator>> (istream& i, vector<T>& v) {
  for (auto& x : v) i >> x;
  return i;
}

istream& operator>> (istream& i, pair<int, int>& p) {
  i >> p.first >> p.second;
  return i;
}



int main() {
  ios::sync_with_stdio(false);
   long long n, m;
  cin >> n >> m;
  vector< long long> c(n + 1);
  vector<vector<int>> e(n + 1);
  for ( long long i = 0; i < m; ++i) {
     long long u, v;
    cin >> u >> v;
    e[u].push_back(v);
    e[v].push_back(u);
    --c[u];
    ++c[v];
  }
  
  //cerr << "e " << e << endl;
  
  long long o = 0;
  vector<bool> v(n + 1);
  vector<int> q;
  for (int s = 1; s <= n; ++s) if (!v[s]) {
      // cerr << "s: " << s << endl;
      bool ok = true;
      int count = 0;
      q.push_back(s);
      while (q.size()) {
        int x = q.back();
        q.pop_back();
        // cerr << "checking x " << x << endl;
        if (v[x]) continue;
        // cerr << "visiting x " << x << endl;
        v[x] = true;
        ok &= c[x] == 0;
        count += e[x].size();
        for (int y : e[x]) {
          // cerr << "pushing y " << y << endl;
          q.push_back(y);
        }
      }
      // cerr << "s " << s << " ok " << ok << " count " << count << endl;
      o += ok && count > 1;
    }
  
  long long hi = 0;
  for ( long long i = 0; i <= n; ++i) {
    if (c[i] > 0) hi += c[i];
  }
  if (o == 0) { cout << max(0ll, hi- 1) << endl; }
  else if (hi == 0) { cout << max(0ll, o - 1) << endl; }
  else { cout << max(0ll, hi + o - 1) << endl; }

  return 0;
}