#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream cin("dfs.in");
ofstream cout("dfs.out");
vector<int> graf[100001];
queue<int> coada;
int i,j,ok,x,y,n,m,cont;
bool fol[100001];
int main()
{
    cin>>n>>m;//n = noduri, m=muchii
    for(i=1; i<=m; i++)
        cin>>x>>y, graf[x].push_back(y);
    for(i=1; i<=n; i++)
       {
           if(!fol[i])
           {
               fol[i]=1; cont++; coada.push(i);
               while(!coada.empty())
               {
                   ok=coada.front(); coada.pop();
                   for(j=0; j<graf[ok].size(); j++)
                       if(!fol[graf[ok][j]])
                       {
                           fol[graf[ok][j]]=1;
                           coada.push(graf[ok][j]);
                       }
               }
           }
       }
    cout<<cont;
}