#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;

ifstream in("dfs.in");
ofstream out("dfs.out");
const int NMax = 100000;
vector <int> ad[NMax + 1];
bool viz[NMax + 1];
int n, m, S, componenteConexe;

void construire(int m, vector <int> ad[NMax + 1])
{
    int x, y;
    for (int i = 1; i <= m; i++)
    {
        in >> x >> y;
        ad[x].push_back(y);
    }
}

void dfs(int S){
    viz[S] = 1;
    for (int i = 0; i < ad[S].size(); i++) {
        int vecin = ad[S][i];
        if (!viz[vecin]) {
            dfs(vecin);
        }
    }
}

int main(){
    in >> n >> m;
    construire(m, ad);
    for (int i = 1; i <= n; i++) {
        if (!viz[i]){
            dfs(i);
            componenteConexe++;
        }
    }
    cout << componenteConexe;
    in.close();
    return 0;
}