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

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

int lst[1001], vf[1001], urm[1001], nr;
bool viz[1001];

void adauga (int x, int y)
{
nr++;
vf[nr] = y;
urm[nr] = lst[x];
lst[x] = nr;
}

void dfs (int x){
    viz[x] = true;
    int y, p;
    p = lst[x];
    while (p != 0){
        y = vf[p];
        if (!viz[y]) dfs(y);
        p = urm[p];
    }
}

int main()
{
    int n, m;

    in >> n >> m;

    for (int i = 1; i <= m; i++)
    {
        int x, y;
        in >> x >> y;
        adauga(x, y);
    }
    int contor = 0;
    for (int i = 1; i <= m; i++)
    {
        if (viz[i] == false) dfs(i);
        contor++;
    }

    out << contor;
    return 0;
}