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

#define NMAX (int)1e5 + 6

void DFS (int node, int n, std::vector<int> adj[NMAX], std::vector<bool>& p) {
        //start[node] = ++timestamp;                      // start visiting its subtree
        // [optional] color[node] = gray; 

        for (auto& vecin : adj[node]) {                      // for each neighbour
        if (p[vecin] == false) {                     // or [optional] color[neigh] = white;
            p[vecin] = node;                        // save parent
            DFS(vecin, n, adj, p);  // continue traversal
        }
        }
                    // finish visiting its subtree
}

// [ATENTIE] NU modifica functia main!
int main() {

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


    // n = numar de noduri, m = numar de muchii/arce
    int n, m;
    fin >> n >> m;
    // adj[node] = lista de adiacenta a nodului node
    // exemplu: daca adj[node] = {..., neigh, ...} => exista arcul (node, neigh)
    vector<int> adj[NMAX];
     for (int i = 1, x, y; i <= m; i++) {
            fin >> x >> y; // arc (x, y)
            adj[x].push_back(y);
    }
    std::vector<bool> p(n + 1, false);
    int nr = 0;
    for (int i = 1; i <= n; i++) {
        if (p[i] == false) {
            p[i] = true;
            DFS(i, n, adj, p);
            nr++;
        }
    }
    fout << nr;
    return 0;
}