#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

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

int n,m,nr_componente=0,viz[100005];

vector <int> G[100005];

void citire_graf()
{
    for(int i=1;i<=m;++i)
    {
        int x,y;
        f>>x>>y;
        G[x].push_back(y);
    }
}

void parcurgere_adancime(int nod)
{
    viz[nod]=nr_componente;
    for(int i=0;i<G[nod].size();++i)
        if(viz[G[nod][i]]==0)
            parcurgere_adancime(G[nod][i]);
}

int main()
{
    f>>n>>m;
    citire_graf();
    for(int i=1;i<=n;++i)
    {
        if(viz[i]==0)
        {
            nr_componente++;
            parcurgere_adancime(i);
        }
    }
    g<<nr_componente;
    return 0;
}