#pragma region Template
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
#pragma endregion Template

vector<vector<int>> adj;
vector<bool> visited;

void dfs(int curr_node) {
    visited[curr_node] = true;
    for (auto& curr_vertex : adj[curr_node])
        if (!visited[curr_vertex])
            dfs(curr_vertex);
}

int main() {
    int n, m;
    fin >> n >> m;

    adj.resize(n), visited.resize(n);

    for (int i = 0; i < m; ++i) {
        int x, y;
        fin >> x >> y;
        --x, --y;

        adj[x].push_back(y);
    }

    int comp_conexe = 0;
    for (int i = 0; i < n; ++i) {
        if (!visited[i]) {
            ++comp_conexe;
            dfs(i);
        }
    }

    fout << comp_conexe;

    return 0;
}