#include <fstream>
#include <vector>

using namespace std;

ifstream fin("dfs.in");
ofstream fout("dfs.out");

int nrConexe = 0;
bool viz[100005];
vector<int> Muchii[100005];

void DFS(int nod){
    viz[nod] = 1;
    for(int i = 0; i < Muchii[nod].size(); ++i)
        if(!viz[Muchii[nod][i]])
            DFS(Muchii[nod][i]);
}

int main()
{
    int n, m;
    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]){
            ++nrConexe;
            DFS(i);
        }
    }
    fout << nrConexe << '\n';
    return 0;
}