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

std::ifstream in("dfs.in");
std::ofstream out("dfs.out");

int n, m;
int marked[100005];

std::vector<int> g[100005];
std::queue<int> dfs;

int Dfs(int node){
//    std::cout << "Marked node " << node << '\n';
    marked[node]=1;
    for(int i = 0; i < g[node].size();i++) {
        int new_node = g[node][i];
        if (!marked[new_node])
            Dfs(new_node);
    }
}

int main() {



    in >> n >> m;
    for (int i = 0; i < m; i++)
        {
            int a, b;
            in >> a >> b;
            g[a].push_back(b);
        }

    int cont = 0;

    for(int i = 1; i <= n; i++)
    {
        if(!marked[i])
        {
            Dfs(i);
            cont++;
        }

    }
    out << cont;
    return 0;
}