#include <bits/stdc++.h>
using namespace std;

class Task {
public:
    void solve() {
        read_input();
        print_output();
    }

private:
    // numarul maxim de noduri
    static constexpr int NMAX = (int)1e5 + 5; // 10^5 + 5 = 100.005

    int n, m;
    vector<int> adj[NMAX];

    void read_input() {
        ifstream fin("dfs.in");
        fin >> n >> m;
        for (int i = 1, x, y; i <= m; i++) {
            fin >> x >> y; // arc (x, y)
            adj[x].push_back(y);
        }
        fin.close();
    }


    void DFS_RECURSIVE(int node, vector<int> &p) {
        for (auto neigh : adj[node]) {
            if (p[neigh] == 0) {
                p[neigh] = node;
                DFS_RECURSIVE(neigh, p);
                
            }
        }
    }
    int get_result() {
        vector<int> p(n + 1);
        int nr = 0;
        for (int i = 1; i <= n; i++) {
            p[i] = 0;
        }
        for (int i = 1; i <= n; i++) {
            if (p[i] == 0) {
                p[i] = i;
                nr++;
                DFS_RECURSIVE(i, p);
            }
        }
        
    return nr;
    }

    void print_output() {
        ofstream fout("dfs.out");
        fout << get_result() << '\n';
        fout.close();
    }
};

int main() {
    auto* task = new (nothrow) Task();
    if (!task) {
        cerr << "new failed: WTF are you doing? Throw your PC!\n";
        return -1;
    }
    task->solve();
    delete task;
    return 0;
}