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

static constexpr int NMAX = (int)1e5 + 5;  // 10^5 + 5 = 100.005
vector<int> adj[NMAX];
void dfs(int node, vector<int> &visited) {
    for (auto neight : adj[node]) {
        if (visited[neight] == 0)
            dfs(neight, visited);
    }
    visited[node] = 1;
}
// [ATENTIE] NU modifica functia main!
int main() {
    int n, m;

    ifstream fin("dfs.in");
    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();

    int nr = 0;
    vector<int> visited(n + 1, 0);
    for (int i = 1; i <= n; i++)
        if (visited[i] == 0) {
            dfs(i, visited);
            nr++;
        }

    ofstream fout("dfs.out");
    fout << nr;
    fout.close();

    return 0;
}