#include<bits/stdc++.h>
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");

const int Nmax = 100005;

list<int> G[Nmax];
bitset<Nmax> viz;
int n, m, nr_comp, x, y, i;

void citire() {

    f >> n >> m;

    while(m--){

        f >> x >> y;

        G[x].push_back(y);
    }
}

void dfs(int nod) {

    viz[nod] = true;

    list<int>::iterator it;

    for(it = G[nod].begin(); it != G[nod].end(); ++it)
        if(!viz[*it])
            dfs(*it);
}

int main(){

    citire();

    for(i = 1; i <= n; ++i)
        if(!viz[i]) {

            nr_comp++;
            dfs(i);
        }

    g << nr_comp;

    return 0;
}