#include<bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 100010;
int n, m, in[MAXN], out[MAXN], ans, f[MAXN];
vector<int> cd[MAXN];
int dfs(int x) {
//	cout << x << endl;
	if(!out[x]) {
		ans ++;
//		cout << 1;
		f[x] = 1;
		return 1;
	}
	if(f[x]) {
		ans += f[x];
		return f[x];
	}
	for(int i = 0; i < cd[x].size(); i ++) {
		int u = cd[x][i];
//		cout << ' ' << u << endl;
		dfs(u);
		f[x] += f[u];
	}
	return f[x];
}
signed main() {
	freopen("chain_2016.in", "r", stdin);
	freopen("chain_2016.out", "w", stdout);
	cin >> n >> m;
	for(int i = 1; i <= m; i ++) {
		int x, y;
		cin >> x >> y;
		cd[x].push_back(y);
		in[y] ++;
		out[x] ++;
	}
	for(int i = 1; i <= n; i ++) {
//		cout << out[i] << ' ';
		if(in[i] == 0) {
			dfs(i);
			if(!out[i]) {
				ans --;
			}
		}
	}
	cout << ans;
    return 0;
}