#include <fstream>
#include <vector>

using namespace std;
const int NMAX = 100000;
vector<int> graf[1 + NMAX];
bool vizitat[1 + NMAX];

void dfs(int nodCrt)
{
    vizitat[nodCrt] = true;

    for (int i = 0; i < graf[nodCrt].size(); i++)
    {
        int vecin = graf[nodCrt][i];

        if(!vizitat[vecin])
            dfs(vecin);
    }
}

int main()
{
    ifstream in("dfs.in");
    ofstream out("dfs.out");

    int n, m;
    in >> n >> m;
    for (int j = 1; j <= m; j++)
    {
        int x, y;
        in >> x >> y;
        graf[x].push_back(y);
    }

    int nrCompCon = 0;
    for (int i = 1; i <= n; i++)
    {
        if (!vizitat[i])
        {
            nrCompCon++;
            dfs(i);
        }
    }

    out << nrCompCon << '\n';

    return 0;
}