#include<fstream>
#include<vector>
using namespace std;
   
int viz[100000];
vector <long> v[100000];
     
void dfs(long nod)
{viz[nod]=1;
 for(long i=0;i<v[nod].size();i++)
   if(viz[v[nod][i]]==0)  dfs(v[nod][i]);
}  
     
int main()
{long n,m,nr=0,x,y;
 ifstream f("dfs.in");
 f>>n>>m;
 for(long i=1;i<=m;i++)
    {f>>x>>y;
     v[x].push_back(y);
     //v[y].push_back(x);
     }
 f.close();
 for(long i=1;i<=n;i++)
   if(viz[i]==0)
     {nr++;
      dfs(i);
      }
 ofstream g("dfs.out");
 g<<nr;     
 g.close();
 return 0;
}