#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

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

bool visit[100001];

vector <int> v[100001];

void DFS(int x)
{
    for(int i = 0; i < v[x].size(); i++)
        if(visit[v[x][i]] == 0)
        {
            DFS(v[x][i]);
            visit[v[x][i]] = 1;
        }

}

int main()
{
    int n, m, ct = 0, x, y;
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        fin >> x >> y;
        v[x].push_back(y);
    }
    for(int i = 1; i <= n; i++)
    {
        if(visit[i] == 0)
        {
            visit[i] = 1;
            DFS(i);
            ct++;
        }
    }
    fout << ct;
    return 0;
}