#include <fstream>
#include <vector>
#define NMAX 100000

using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
int n, m, nrc;
vector<int> G[NMAX];
bool uz[NMAX];
void citire();
void DFS(int start);
int main()
{
    int i;
    citire();
    for (i=1; i<=n; i++)
         if (uz[i]==0)
            {DFS(i);
             nrc++;}
    fout<<nrc<<'\n';
    return 0;
}

void citire()
{
    int i, x, y;
    fin>>n>>m;
    for (i=0; i<m; i++)
        {
          //arc
          fin>>x>>y;
          G[x].push_back(y);
        }
}

void DFS(int start)
{
    int i;
    uz[start]=1;
    for (i=0; i<G[start].size(); i++) //nu imi fac probleme ca size se calculeaza constant!
        if (uz[G[start][i]]==0)
           DFS(G[start][i]);

}