#include <iostream>
#include <fstream>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#define NMax 100001

using namespace std;

ifstream fin("dfs.in");
ofstream fout("dfs.out");

vector<int> v[NMax];
int viz[NMax];
int n, m;

void CitireGraph()
{
    int x, y;
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        fin >> x >> y;
        if( x != y )
            v[x].push_back(y);
    }
}

void AfisareGraph()
{
    for(int i = 1; i <= n; i++)
    {
        fout << i << ":";
        for(auto j : v[i])
            fout << j << " ";
        fout << endl;
    }

}

void DFS(int a, int k) // a -> varful de pornire; k -> numarul alementului conex;
{
    viz[a] = k;
    for(auto i : v[a])
        if( viz[i] == 0 )
            DFS(i, k);
}

int main()
{
    int k = 0;
    CitireGraph();
    for(int i = 1; i <= n; i++)
    {
        if(viz[i] == 0)
            DFS(i, ++k);
    }
    fout << k;
    return 0;
}