#include <bits/stdc++.h>
#define NMAX 100009
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
int n,m,i,cate;
//struct vf{int x;int c;};

vector <int> g[NMAX];
bool uz[NMAX];
void citire();
void dfs(int k);
int main()
{
   citire();
   for(i=1;i<=n;i++)
    if(!uz[i])
    {dfs(i);cate++;}
 fout<<cate;
    return 0;
}
void citire()
{
  int i,x,y,cost;
  //vf el;
  fin>>n>>m;
  for(i=1;i<=m;i++)
    {
     fin>>x>>y;
     //el.x=y;el.c=cost;
     g[x].push_back(y);
     //a[y].push_back(x);
    }

}
void dfs(int k)
{int i;
 uz[k]=1;
 //fout<<k<<" ";
 for(i=0;i<g[k].size();i++)
    if(!uz[g[k][i]])
    {
      dfs(g[k][i]);
    }
}