#include <fstream>
#include <stack>
#include <vector>
using namespace std;
int n,m,i;
vector<int> v[100002];
int viz[100002];
int sol = 0;

void dfs(int nod)
{
    int nr_v = v[nod].size();
    for(int v : v[nod])
    {
        if(viz[v] == 0)
        {
            viz[v] = 1;
            dfs(v);
        }
    }

}
int main()
{
    ifstream f("dfs.in");
    ofstream g("dfs.out");
    f >> n >> m;
    for( i=0;i<m;i++)
    {
        int x ,y;
        f >> x >> y;
        v[x].push_back(y);
    }
    for(i=1;i<=n;i++)
    {
        if(viz[i] == 0)
        {
            viz[i] = 1;
            dfs(i);
            sol++;
        }
    }
    g << sol;
    f.close();
    g.close();
    return 0;
}