#include <fstream>
#include <vector>
#include <string.h>

using namespace std;

fstream f("dfs.in",ios::in);
fstream g("dfs.out",ios::out);

int const nmax=100005;

vector <int> a[nmax];

int n,m,i,j,x,y,comp,viz[nmax];

void citire()
{
    f>>n>>m;
    for (i=1;i<=m;i++)
    {
        f>>x>>y;
        a[x].push_back(y);
    }
}

void rezolvare(int nc)
{
    for (vector<int>::iterator it=a[nc].begin();it!=a[nc].end();++it)
    {
        if(!viz[*it])
        {
            viz[*it]=1;
            rezolvare(*it);
        }
    }

}

int main()
{
    citire();
    comp=0;
    memset(viz,0,sizeof(viz));
    for (i=1;i<=n;i++) if (!viz[i]) {
                                        comp++;
                                        viz[i]=1;
                                        rezolvare(i);
    }
    g<<comp;

    return 0;
}