#include <iostream>
#include <fstream>
#include <vector>
#define NMAX 100001
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");
vector <int> G[NMAX];
bool viz[NMAX];
int cont,n,m;
void DFS(int x)
{
    viz[x]=1;
    for(int i=0;i<G[x].size();++i)
    {
        if(viz[G[x][i]]==0)
            DFS(G[x][i]);
    }
}
int main()
{
    f>>n>>m;
    int x,y;
    for(int i=1;i<=m;++i)
    {
        f>>x>>y;
        G[x].push_back(y);
    }
     for(int i=1;i<=n;++i)
    {
        if(viz[i]==0)
        {
            DFS(i);
            ++cont;
        }
    }
    g<<cont;



    return 0;
}