#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;

ifstream in("dfs.in");
ofstream out("dfs.out");

int const maxim = 100005;

vector<int> stocare[maxim];
queue<int> coada;

bool vizitat[maxim];

int n, m;

void citire() {
	in >> n >> m;
	int a, b;
	for (int i = 1; i <= m; i++) {
		in >> a >> b;
		stocare[a].push_back(b);
	}
}

void dfs(int nodstart) {
	vizitat[nodstart] = true;
	for (size_t i = 0; i < stocare[nodstart].size(); i++) {
		if (!vizitat[stocare[nodstart][i]])dfs(stocare[nodstart][i]);
	}
}

void solve() {
	int conexe = 0;
	for (int i = 1; i <= n; i++) {
		if (!vizitat[i]) {
			conexe++;
			dfs(i);
		}
	}
	out << conexe;
}

int main() {
	citire();
	solve();
	return 0;
}