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

using namespace std;

void dfs(const vector<vector<int>>& graph, vector<bool>& visited, int start)
{
    queue<int> q;
    
    visited[start] = true;
    q.push(start);
    
    while(!q.empty())
    {
        int node = q.front();
        q.pop();
        
        for(int neigh: graph[node])
        {
            if(!visited[neigh]) {
                q.push(neigh);
                visited[neigh] = true;
            }
        }
    }
}

int main() 
{
    ifstream fin("dfs.in");
    ofstream fout("dfs.out");
    int n, m, s;
    
    fin >> n >> m;
    vector<vector<int>> graph(n + 1);
    for(int i = 0; i < m; i++)
    {
        int a, b;
        
        fin >> a >> b;
        graph[a].push_back(b);
    }
    vector<bool> visited(n + 1);
    int conexe = 0;
    for(int i = 1; i <= n; i++) 
    {
        if(!visited[i]) 
        {
            dfs(graph, visited, i);
            ++conexe;
        }
    }
    fout << conexe;
    
    return 0;
}