#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <string.h>
using namespace std;

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

constexpr int NX = 100010;
int n, m, viz[NX], contor;
vector <int> V[NX];
stack <int> S;

void dfs(int nod)
{
    S.push(nod); //bag in coada primul nod
    while(!S.empty())
    {
        int nodCurent = S.top();
        S.pop();
        if(viz[nodCurent] == 0) //caut prin vecini si daca gasesc nevizitati ii bag
        {
            viz[nodCurent] = contor;
            for(int i=0; i<V[nodCurent].size(); ++i)
            {
                S.push(V[nodCurent][i]);
            }
        }
    }
}
int main()
{
    fin>>n>>m; //citesc chestiile
    int x, y;
    for(int i=1; i<=m; ++i)
    {
        fin>>x>>y;
        V[x].push_back(y);
    }

    for(int i=1; i<=n; ++i) //parcurg din fiecare nod si leg componentele
    {
        if(viz[i]==0)
        {
            contor++; //cresc contorul pt fiecare componenta gasita
            dfs(i);
        }
    }

    fout<<contor;
    return 0;
}