#include <iostream>
#include <fstream>

using namespace std;

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

int n,m,ma[1005][1005],viz[1005],nrc;

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

void parcurgere_adancime(int nod)
{
    viz[nod]=nrc;
    for(int i=1;i<=n;++i)
    {
        if(ma[nod][i]==1 && viz[i]==0)
            parcurgere_adancime(i);
    }
}

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