/* finding the number of connected components through a depth first search */
#include <bits/stdc++.h>

using namespace std;

const int NMAX = 123000;

int n, m;
vector<int> adj[NMAX];
bool visited[NMAX];

void dfs(int u) {
	visited[u] = true;
	for (int v : adj[u]) {
		if (!visited[v]) {
			dfs(v);
		}
	}
}

int main() {
	ios_base::sync_with_stdio(false);
	freopen("dfs.in", "r", stdin);
	freopen("dfs.out", "w", stdout);
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		int x, y;
		cin >> x >> y;
		adj[x].push_back(y);
	}
	for (int i = 0; i < NMAX; i++) {
		visited[i] = false;
	}
	int ans = 0;
	for (int i = 1; i <= n; i++) {
		if (!visited[i]) {
			dfs(i);
			ans++;
		}
	}
	cout << ans << endl;
	return 0;
}