#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

//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);
/*
	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;
		int a = gt[b][0];
		deg[a]++;
		from[b]=a;
	}

	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;
}