#include <queue>
#include <vector>
#include <fstream>
#include <iostream>
#include <algorithm>

using namespace std;

ifstream f("dfs.in");
ofstream g("dfs.out");

int n, m, nr;

vector<int> v;

vector<vector<int> > graph;

bool visited[100001] = { false };

void dfs(int node)
{
    visited[node] = true;
    for (auto& i : graph[node]) {
        if (!visited[i])
            dfs(i);
    }
}

int main()
{
    f >> n >> m;
    v.resize(n + 1);
    graph.resize(n + 1);
    for (int i = 1; i <= m; ++i) {
        int a, b;
        f >> a >> b;
        graph[a].push_back(b);
    }

    for (int i = 1; i <= n; ++i) {
        if (!visited[i]) {
            ++nr;
            dfs(i);
        }
    }
    g << nr;
    return 0;
}