#include <iostream>
#include <fstream>
#include <vector>
#include <queue>

using namespace std;

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

static constexpr int NMAX = (int)1e5 + 5;
vector<int> adj[NMAX];

void dfs(int node, vector<int> &visited) {
    visited[node] = 1;
    for (int i = 0; i < adj[node].size(); i++) {
        if (visited[adj[node][i]] == 0) {
            dfs(adj[node][i], visited);
        }
    }
}

int main() {
    int N, M;
    fin >> N >> M;
    for (int i = 1; i <= M; i++) {
        int x, y;
        fin >> x >> y;
        adj[x].push_back(y);
    }

    vector<int> visited(N + 1, 0);
    int contor = 0;

    for (int i = 1; i <= N; i++) {
        if (visited[i] == 0) {
            //todo
            contor++;
            dfs(i, visited);
        }
    }

    fout << contor << '\n';
}