#include <bits/stdc++.h>
#include <unordered_map>
using namespace std;
#define ll long long 
#define ull unsigned long long 
#define nmax 100006
#define MOD 9901 
#define INF 2123456789
//#define fin cin 
//#define fout cout 

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

int n, m, cnt;
vector <int> L[nmax];
int viz[nmax];

void DFS(int k)
{
	viz[k] = 1;
	for (int i : L[k])
		if (!viz[i])
			DFS(i);
}

int main()
{
	int  i, j;
	fin >> n >> m;
	while (m--)
	{
		fin >> i >> j;
		L[i].push_back(j);
	}
	for (i = 1; i <= n; i++)
		if (!viz[i])
		{
			++cnt;
			DFS(i);
		}
	fout << cnt << "\n";
	fin.close();
	fout.close();
	return 0;
}