#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>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  dsu d(n);
  VI indeg(n), outdeg(n);
  rep(_, m) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    d.merge(u, v);
    outdeg[u]++;
    indeg[v]++;
  }
  VI a;
  for(const auto& g : d.groups()) {
    int ai = 0;
    if (g.size() == 1 && indeg[g[0]] == 0) continue;
    for(int v: g) {
      if (indeg[v] < outdeg[v]) ai += outdeg[v] - indeg[v];
    }
    a.emplace_back(ai);
  }
  ll ans = 0;
  if (a.size() == 1) {
    ans = a[0];
  } else {
    for(int& ai: a) chmax(ai, 1);
    ans = accumulate(all(a), 0LL);
  }
  if (ans) ans--;
  cout << ans << '\n';
}