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

using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
vector<int> G[100005];
int n,m;
int viz[100005];

void DFS(int k)
{
     viz[k]=1;
     for(int i=1;i<=n;i++)
        if(find(G[k].begin(),G[k].end(),i)!=G[k].end() and !viz[i])
            DFS(i);
}
int main()
{
     int nr_conex=0;
     int i,j;
     fin>>n>>m;
     while(fin>>i>>j){
        G[i].push_back(j);
        //G[j].push_back(i);
     }
    for(int i=1;i<=n;i++){
        if(!viz[i])
           {
             DFS(i);
             nr_conex++;
           }

    }
    fout<<nr_conex;

}