#include <fstream>
#include <iostream>
#include <string>
#include <vector>
#include <bitset>
#include <deque>


using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");


#define VERTECES 100001

vector<int> graph[VERTECES];
bool viz[VERTECES];

void dfs(int node) {

	viz[node] = 1;
	for (int i = 1; i <= graph[node].size(); ++i) {
		dfs(graph[node][i - 1]);
	}
}

int main()
{
	int vertices, edges, source;
	f >> vertices >> edges;
	int x, y;
	for (int i = 1; i <= edges; ++i) {
		f >> x >> y;
		graph[x].push_back(y);
	}
	int nr = 0;
	for (int i = 1; i <= vertices; ++i) {
		if (!viz[i]) {
			++nr;
			dfs(i);
		}
	}
	g << nr;

	f.close();
	g.close();
	return 0;
}