#include<fstream>
#include<vector>
#include<deque>
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
const int NMAX=100005;
bool viz[NMAX];
vector<int>v[NMAX];
int n,m,cnt;
void adiacenta()
{
    int i,j;
    fin>>n>>m;
    while(m--)
    {
        fin>>i>>j;
        v[i].push_back(j);
    }
}
void BFS(int k)
{
    deque<int>nod;
    nod.push_back(k);
    while(nod.empty()==false)
    {
        for(auto i:v[nod.front()])
            if(viz[i]==0)
            {
                nod.push_back(i);
                viz[i]=1;

            }
        nod.pop_front();
    }
}
void componenteconexe()
{
    int i;
    for(i=1;i<=n;++i)
        if(viz[i]==0)
        {
            ++cnt;
            BFS(i);
        }
    fout<<cnt;
}
int main()
{
    adiacenta();
    componenteconexe();
}