/// cu dfs
#include <fstream>
#include <vector>
using namespace std;
vector <int> v[100];
int n,m,nr_conex,G[100],viz[100],a,b;
void dfs(int start)
{

    int i;
    viz[start]=1;
    for(i=0;i<G[start];i=i+1)
        if(viz[v[start][i]]==0)
        dfs(v[start][i]);
}
int main()
{
    ifstream f("dfs.in");
    ofstream g("dfs.out");

    f>>n>>m;
    int i;
    for(i=1;i<=m;i=i+1)
    {
        f>>a>>b;
        v[a].push_back(b);
    }
    for(i=1;i<=n;i=i+1)
    G[i]=v[i].size();

    for(i=1;i<=n;i=i+1)
    if(viz[i]==0)
    {
        nr_conex++;
        dfs(i);
    }
g<<nr_conex;

    return 0;
}