#include<fstream>
using namespace std;
#define nmax 100001

struct nod{int x; nod *next;};
nod *lista[nmax];
int n,i,m,a,b,viz[nmax],nr;

void dfs(int start) {
  viz[start]=1;
  for (nod *p=lista[start];p!=NULL;p=p->next)
    if (!viz[p->x]) 
      dfs(p->x);
}   

int main() {
  ifstream f("dfs.in",ifstream::in);
  ofstream g("dfs.out",ifstream::out);
  f>>n>>m;
  for (i=0;i<m;i++) {
    f>>a>>b;
	nod *q=new nod;
	q->x=b;
	q->next=lista[a];
	lista[a]=q;
	}
  for (i=1;i<=n;i++)
    if (!viz[i]) {
      nr++;
      dfs(i);
      }
  g<<nr;
  return 0;
}