#include fstream
#include vector
#include stack

int main()
{
    int n, m;
    stdvectorstdvectorint la;
    stdifstream in(dfs.in);
    in  n  m;
    for (int i = 0; i  n; i ++) {
        la.push_back(stdvectorint());
    }
    for (int i = 0; i  m; i ++) {
        int x, y;
        in  x  y;
        x --;
        y --;
        la[x].push_back(y);
    }
    in.close();
    stdvectorbool este_parcurs(n, false);
    int nr_comp_conexe = 0;
    for (int i = 0; i  n; i ++) {
        if (este_parcurs[i]) {
            continue;
        }
        nr_comp_conexe ++;
        stdstackint s;
        s.push(i);
        este_parcurs[i] = true;
        while (!s.empty()) {
            int act = s.top();
            s.pop();
            for (auto vec la[act]) {
                if (este_parcurs[vec]) {
                    continue;
                }
                este_parcurs[vec] = true;
                s.push(vec);
            }
        }
    }
    stdofstream out(dfs.out);
    out  nr_comp_conexe;
    out.close();
        
    return 0;
}