#include <fstream>
#include <vector>
#include <list>
#include <queue>

using namespace std;

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

int  n, m, op, x, y, k, s, v;
int sol[50001], viz[100001];
vector<int> G[100001];


void dfs(int t)
{
    viz[t] = 1;
    for (int i = 0; i < (int)G[t].size(); i++)
    {
        int j = G[t][i];
        if (viz[j] == 0)
            dfs(j);
    }
}
int main()
{
    f >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        f >> x >> y;
        G[x].push_back(y);
    }
    int nr = 0;
    for (int i = 1; i <= n; i++)
    {
        if (!viz[i])
        {
            nr++;
            dfs(i);
        }
    }

    g << nr << " ";

    return 0;
}