#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");


int n, m, s, i, j;
void addEdge(vector<vector<int>>& adj, int i, int j)
{
    adj[i].push_back(j);
}

void display(const vector<vector<int>> adj)
{
    for(int i = 0; i < n; i++)
    {
        cout << i << ": ";
        for(int j : adj[i])
        {
            cout << j << " ";
        }
        cout << endl;
    }
}
vector<int> bfs(vector<vector<int>> &adj, int s, int n)
{
    vector<int>res(n, -1);
    queue<int>q;
    vector<int>visited(n, false);
    visited[s] = true;
    q.push(s);
    res[s] = 0;

    while(!q.empty())
    {
        int current = q.front();
        q.pop();

        for(int x : adj[current])
        {
            if(!visited[x])
            {
                q.push(x);
                visited[x]=true;
                res[x] = res[current] + 1;
            }
        }
    }
    return res;

}

void dfs(vector<vector<int>> &adj, vector<bool>&visited,  int s, int n)
{
    visited[s] = true;
    for(int i : adj[s])
    {
        if(visited[i] == false)
        {
            dfs(adj, visited,  i, n);
        }
    }

}
int main()
{
    fin >> n >> m;
    vector<vector<int>> adj(n);

    for(int p = 1; p <= m; p++)
    {
        fin >> i >> j;
        addEdge(adj, i-1, j-1);
    }


    vector<bool> visited(n, false);
    int cnt = 0;
    for(i = 0; i < n; i++)
    {
        if(visited[i] == false)
        {
            cnt ++;
            dfs(adj, visited, i, n);
        }
    }

    fout << cnt;

    return 0;
}