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

using namespace std;

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

int n, m, v[NMAX], s=0;
vector <int> G[NMAX];

void citire()
{
    fin>>n>>m;
    int x, y;
    for(int i=1; i<=m; ++i)
    {
        fin>>x>>y;
        G[x].push_back(y);
    }
}
void dfs(int x)
{
    vector <int>::iterator it;
    v[x]=1;
    for(it=G[x].begin(); it!=G[x].end(); ++it)
    {
        if(v[*it]==0)
            dfs(*it);
    }
}
void rezolvare()
{
    for(int i=1; i<=n; ++i)
    {
        if(v[i]==0)
        {
            dfs(i);
            s++;
        }
    }
}
int main()
{
    citire();
    rezolvare();
    fout<<s;
    return 0;
}