#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;
ifstream in("dfs.in");
ofstream out("dfs.out");
vector<int> v[100003];
bool visited[100003]{false};
queue<int> que;
void dfs(int nod)
{
    for(int neighbour : v[nod])
    {
        if (!visited[neighbour] )
        {
            visited[neighbour] = true;
            dfs(neighbour);
        }
    }
}
int main()
{
    int n,m,s;
    in >> n >> m ;
    int x,y;
    for(int i  =0 ; i < m ; i++)
    {
        in >> x >> y;
        v[x].push_back(y);
    }
    int k =0;
    for(int i = 1 ; i <= n ; i++)
        if(!visited[i] )
        {
            visited[i] = true;
            k++;
            dfs(i);
        }
    out<<k;
    return 0;
}