#include <cstdio>
#include <iostream>
#include <vector>
#include <bitset>

using namespace std;

const int MAX_NODURI = 100000;

int nNoduri, nMuchii;
vector<int> muchii[MAX_NODURI];
bitset<MAX_NODURI> isNodVizitat;

void dfs(int nod){
    vector<int>::iterator vecin;
    for(vecin = muchii[nod].begin(); vecin<muchii[nod].end(); ++vecin)
        if(!isNodVizitat[*vecin]){
            isNodVizitat[*vecin] = true;
            dfs(*vecin);
        }
}

int main()
{
    freopen("dfs.in","r",stdin);
    freopen("dfs.out","w",stdout);

    cin >> nNoduri >> nMuchii;

    for (int i=0;i<nMuchii;++i){
        static int x,y;
        cin >> x >> y;
        muchii[x].push_back(y);
    }

    int nComponente = 0;
    for (int i=1; i<=nNoduri; ++i)
        if (!isNodVizitat[i]){
            ++nComponente;
            dfs(i);
        }

    cout << nComponente << '\n';

    return 0;
}