#include <iostream>
#include <vector>
#include <queue>
#include <fstream>
using namespace std;
const int NMAX = 100000;
int n, m, x, y, i, ans;
bool viz[NMAX + 5];
vector <int> g[NMAX + 5];
queue<int> q;
void BFS(int s);
void DFS(int k);
int main() {
    ifstream cin("dfs.in");
    ofstream cout("dfs.out");
    cin >> n >> m;
    for(i = 1; i <= m; ++i) {
        cin >> x >> y;
        g[x].push_back(y);
    }
    
    for(i = 1; i <= n; ++i) {
        if(!viz[i]) {
            ans++;
            DFS(i);
        }
    }
    cout << ans << "\n";
    return 0;
}
void DFS(int k) {
    viz[k] = 1;
    vector<int>:: iterator it;
    for(it = g[k].begin(); it < g[k].end(); ++it) {
        if(!viz[*it]) {
            viz[*it] = true;
            DFS(*it);
        }
    }
}