#include <bits/stdc++.h>
#define MAXN 100005

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

vector<int> v[MAXN];
int n, m;
bool vizitat[MAXN];
int nrComp;

void citire() {
    int x, y;
    fin >> n >> m;
    for (int i = 1; i <= m; i ++) {
        fin >> x >> y;
        v[x].push_back(y);
    }
}

void afisare() {
    for (int i = 1; i <= n; i ++) {
        cout << i << ": ";
        for (auto e : v[i])
            cout << e << ' ';
        cout << endl;
    }
}

void dfs(int nod) {
    vizitat[nod] = true;
    for (auto e : v[nod])
        if (!vizitat[e])
            dfs(e);
}

int main() {
    citire();
    for (int i = 1; i <= n; i ++)
        if (!vizitat[i]) {
            dfs(i);
            nrComp ++;
        }
    fout << nrComp;
//    afisare();
    return 0;
}