#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i, a, n) for (int i = (a); i < (n); i++)
#define per(i, a, n) for (int i = (n) - 1; i >= (a); i--)
#define FOR(i, n) rep(i, 0, (n))
#define fi first
#define se second

template <class E, class I>
bool topo_sort(const E& edges, I& idx, int n) {
	vector<int> indeg(n);
	rep(i,0,n)
		for(auto& e : edges[i])
			indeg[e]++;

	queue<int> q;
	rep(i,0,n) if (indeg[i] == 0) q.push(-i);
	int nr = 0;
	while(q.size() > 0) {
		int i = -q.front();
		idx[i] = nr++;
		q.pop();
		for(auto& e : edges[i])
			if (--indeg[e] == 0) q.push(-e);
	}
	return nr == n;
}

//char endl = '\n';
int main(void) {
	ios_base::sync_with_stdio(false);
	int n, m;
	cin >> n >> m;
	vector<vector<int>> gt(n);
	vector<vector<int>> g(n);
	rep(i,0,m) {
		int a, b;
		cin >> a >> b;
		a--; b--;
		gt[b].push_back(a);
		g[a].push_back(b);
	}
	vector<int> deg(n, 0);
	vector<int> from(n,-1);

	vector<int> idx(n);
	topo_sort(g, idx, n);
/*
	rep(i,0,n) cout << idx[i] << " ";
	cout << endl;

	rep(a,0,n) {
		cout << "a!!!" << a << endl;
		for(auto b : g[a]) {
			cout << b << " ";
		}
		cout << endl;
	}
*/
	rep(b,0,n) {
		if (gt[b].empty()) continue;
		for (auto a : gt[b]) {
			if (from[b] == -1 || idx[a] > idx[from[b]]) {
				from[b] = a;
			}	
		}
		if (from[b] != -1) {
			deg[from[b]]++;
		}
	}
	
//	rep(i,0,n) {
//		cout << i << " from " << from[i] << endl;
//	}

	bool done = false;
	while(!done) {
		done = true;
		rep(a,0,n) {
			if (from[a] == -1) continue;
			if (deg[a] == 0) {
				for (auto b : g[a]) {
					int c = from[b];
					if (deg[c] > 1) {
						from[b] = a;
						deg[c]--;
						deg[a]++;
						done = false;
						break;
					}
				}
			}
		}
	}

	int res = n - 2;
	rep(a,0,n) {
		if (deg[a] == 0) {
			res++;
		}
	}

//	rep(a,0,n) cout << deg[a] << " "; cout << endl;

	cout << (m-res) << endl;
	return 0;
}