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

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

int n, m;
bool vizitat[50005];
vector <int> G[10001];

void Dfs(int nod);

int main()
{
    fin >> n >> m;
    int x, y;
    for (int i = 1; i <= m; ++i)
    {
        fin >> x >> y;
        G[x].push_back(y);
    }
    int cnt = 0;
    for (int i = 1; i <= n; ++i)
    {
        if (!vizitat[i])
        {
            Dfs(i);
            cnt++;
        }
    }

    fout << cnt;
}
void Dfs(int nod)
{
    vizitat[nod] = true;
    for (int i = 0; i < G[nod].size(); ++i)
    {
        int nou = G[nod][i];
        if (!vizitat[nou])
            Dfs(nou);
    }
}