#include <iostream>
#include <fstream>
#include <queue>
using namespace std;

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

vector<int> LA[100001]; // graf neorientat
int n, m, viz[100001], nrCc;

void dfs(int x, int p)
{
    viz[x]=1;
    for (int i=0; i<LA[x].size(); i++)
    {
        if (!viz[LA[x][i]])    // else ciclu in graf
        {
            viz[LA[x][i]] = 1;
            dfs(LA[x][i], x);
        }
    }
}


int main() {

    int x, y;
    fin >> n >> m;

    for (int i=1; i<=m; i++) {
        fin >> x >> y;
        LA[x].push_back(y);
    }

    for(int i=1;i<=n;++i) {
        if (viz[i] == 0) // am gasit o componenta conexa noua
        {
            ++nrCc;
            dfs(i, -1);
        }
    }
    fout << nrCc << endl;
    
    return 0;
}