// dfs.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <fstream>
#include <vector>
#include <queue>

using namespace std;
ifstream cin("dfs.in");
ofstream cout("dfs.out");

int N, M, S;

vector <int>G[100005];
int viz[100005] = { 0 }, dist[100005] = { 0 };
queue<int>Q;
int nrComp = 0;

void dfs(int i)///practic fac "fill" pe componenta conexa din care face parte nodul i
{
    viz[i] = 1;
    for (auto k : G[i])
    {
        if (viz[k] == 0)
        {
            viz[k] = 1;
            dfs(k);
        }
    }
}


int main()
{
    cin >> N >> M;
    for (int i = 0; i < M; i++)
    {
        int x, y;
        cin >> x >> y;
        G[x].push_back(y);
    }

    for (int i = 1; i <= N; i++)
    {
        if (viz[i] == 0)
        {
            nrComp++;
            dfs(i);
        }
    }
    cout << nrComp;

    return 0;
}