#include <fstream>
#include <vector>
#include <bitset>
#include <queue>
#define ll long long
using namespace std;

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

const int NMAX = 1e5;
int n, m;
vector<int> G[NMAX + 1];
bool viz[NMAX + 1];

void DFS(int Nod)
{
    viz[Nod] = 1;
    for(int Nod_Vecin : G[Nod])
        if(!viz[Nod_Vecin])
            DFS(Nod_Vecin);
}


int main()
{
    cin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        int x, y;
        cin >> x >> y;
        G[x].push_back(y);
    }

    int componente_conexe = 0;
    for(int i = 1; i <= n; i++)
        if(!viz[i])
        {
            componente_conexe++;
            DFS(i);
        }

    cout << componente_conexe;

    return 0;
}