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

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

static constexpr int NMAX = (int)1e5 + 5; // 10^5 + 5 = 100.005
vector<int> adj[NMAX];
int n, m;

void read_input() {
    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(int node, vector<int> &v) {
    v[node] = 1;

    
    for (auto neigh : adj[node]) {
        if (!v[neigh]) {
            DFS(neigh, v);

        }
    }
}

int get_result() {
    vector<int> viz(n+1);
    int comp = 0;
    
    for (int i = 1; i <= n; i++) {
        if (viz[i] == 0) {
            DFS(i, viz);
            comp++;
        }
    }
    return comp;
}

int main() {
    read_input();
    fout << get_result();
}