#include <iostream>
#include <fstream>
using namespace std;
ifstream in("dfs.in");
ofstream out("dfs.out");
int n,m,i,j,v[100][100],x,y,s[100],h;
void citire()
{
    in>>n>>m;
    for(i=i;i<=m;i++)
    {
    in>>x>>y;
    v[x][y]=1;
    }
}
int afisare()
{
    for(i=1;i<=n;i++)
    {for(j=1;j<=n;j++)
    cout<<v[i][j]<<" ";
    cout<<endl;}
}
int DF(int nod)
{
    int k;
    for(k=1;k<=n;k++)
    {
        if((v[nod][k]==1)&&(s[k]==0))
        {
            s[k]=k;
            DF(k);
        }
    }

}
int alt()
{
for(i=1;i<=n;i++)
   {
   if(!s[i])
   {
       s[i]=i;
       DF(i);
       h++;
   }
   }

}
int main()
{
   citire();
   alt();
   out<<h;
}