#include <bits/stdc++.h>
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
int n, m, insule;
bool viz[100002];
vector <int> Muchii[100002];
void DFS(int nod)
{
    viz[nod] = true;
    for (int i = 0; i < Muchii[nod].size(); ++i)
    {
        if (!viz[Muchii[nod][i]])
        {
            DFS(Muchii[nod][i]);
        }
    }
}
int main()
{
    fin >> n >> m;
    for (int i = 1; i <= m; ++i)
    {
        int x, y;
        fin >> x >> y;
        Muchii[x].push_back(y);
    }
    for (int i = 1; i <= n; ++i)
    {
        if (viz[i] == false)
        {
            ++insule;
            DFS(i);
        }
    }
    fout << insule;
}