#include <fstream>
#include <algorithm>
#include <vector>
#include <iostream>
#define NMAX 100005

using namespace std;

ifstream fin("dfs.in");
ofstream fout("dfs.out");
int n, m, i, conex, varf, marc[NMAX];

vector <int> vecini[NMAX];

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

int urmatorulvarf() {
    int i, vf = 0;
    for (i = 1; i <= n and not vf; i++)
        if (not marc[i])
            vf = i;
    conex++;
    return vf;
}

void dfs(int p) {
    int i, y;
    marc[p] = 1;
    for (i = 0; i < vecini[p].size(); i++) {
        y = vecini[p][i];
        if (not marc[y])
            dfs(y);
    }
}

int main() {
    citire();
    varf = 1; conex = 0;
    while (varf) {
        dfs(varf);
        varf = urmatorulvarf();
    }
    fout << conex;
    fout.close();
    return 0;
}