#include <fstream>
#include <vector>
#define MAX_VERTICES 200001
using namespace std;

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

vector<int> adj[MAX_VERTICES];
int visited_vertices[MAX_VERTICES];

void DFS(int current) {
    for (int &neighbor : adj[current]) {
        if (!visited_vertices[neighbor]) {
            visited_vertices[neighbor] = 1;
            DFS(neighbor);
        }
    }
}

int main() {
    int nr_vertices, nr_edges, vertex_a, vertex_b, cc_counter = 0;
    fin >> nr_vertices >> nr_edges;
    for (int i = 0; i < nr_edges; i++) {
        fin >> vertex_a >> vertex_b;
        adj[vertex_a].push_back(vertex_b);
    }
    for (int vertex = 1; vertex <= nr_vertices; vertex++) {
        if (!visited_vertices[vertex]) {
            DFS(vertex);
            ++cc_counter;
        }
    }
    fout << cc_counter << '\n';
    return 0;
}