#include<iostream>
#include<vector>
#include<map>
#include<stack>
#include<fstream>
#include<algorithm>
using namespace std;
std::map<int,vector<int> > nods;
int n,m;
ifstream f("dfs.in");
ofstream g("dfs.out");
void read_nod(){

	int y,x;
	f>>n>>m;
	//cout<<n<<m;

	for(int i=0;i<m;i++)
	{
		f>>x>>y;
		nods[x].push_back(y);
	}
}
void out_date(int n){
	for(int i =1;i<=n;i++)
		{
			vector<int > a;
			a=nods[i];
			cout<<" pentru nodul "<<i<<endl;
			for(int j=0;j<a.size();j++)
				cout<<a[j]<< "  ";
			cout<<endl;
		}
}
map<int,int> nod;
int b[1000];
int DFS(int s){
	int i;
	b[s]=1;
	for(i=0;i<nods[s].size();i++)
	{
		//cout<<nods[s][i];
		if(b[nods[s][i]]==0)
			DFS(nods[s][i]);
	}
//	cout<<s<<" ";
	return 0;
}
int viz[10001];
int main ()
{
	int c;
	read_nod();
	//out_date(n);
	for(int i=1;i<=n;i++)
		if(b[i]==0){
			c++;

			DFS(i);
		}
	g>>c;
			return 0;
}