#include <fstream>
#include <bits/stdc++.h>

using namespace std;

void dfs(int v, bool visited[], vector<int> adj[]) {
    visited[v] = true;
    for (auto m : adj[v]) {
        if (!visited[m])
            dfs(m, visited, adj);
    }
}

int main() {
    ifstream in("dfs.in");
    ofstream out("dfs.out");

    vector<int> adj[100000];
    int n, m;
    in >> n >> m;

    for (int i = 0; i < m; i++) {
        int x, y;
        in >> x >> y;
        adj[x].push_back(y);
    }

    int comp = 0;
    bool  visited[100000] = {false};
    for (int i = 0; i < n; i++) {
        if (!visited[i]) {
            comp++;
            dfs(i, visited, adj);
        }

    }
    
    out << comp;

    in.close();
    out.close();
    return 0;
}