#include <fstream>
#include <iostream>
#include <vector>
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");

int viz[1001];
vector<int> v[1001];

void dfs(int node)
{
    viz[node] = 1;
    for (auto i : v[node])
    {
        if (viz[i] == 0)
        {
            dfs(i);
        }
    }
}
int main()
{
    int n, m;
    fin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int x, y;
        fin >> x >> y;
        v[x].push_back(y);
    }
    int conexe = 0;
    for (int i = 1; i <= n; i++)
    {
        if (viz[i] == 0)
        {
            conexe++;
            dfs(i);
        }
    }
    fout << conexe;
    return 0;
}