#include<fstream>
#include<vector>
using namespace std;
#define nm 100005
int n, m, s, viz[nm];
vector <int> v[nm];
ifstream f("dfs.in");
ofstream g("dfs.out");
void citire()
{
	int x,y;
	f>>n>>m;
	while(f>>x>>y) v[x].push_back(y);
}
void dfs(int s)
{
	int st[nm],p,nod,i,y;
	p=1;
	st[p]=s;
	viz[s]=1;
	while(p>=1)
	{
		nod=st[p];
		
		y=0;
		for(i=0;i<v[nod].size();i++)
		{
			
			if(viz[v[nod][i]]==0){y=v[nod][i];break;}
			
		}
		if(y!=0)
		{
		p++;
		st[p]=y;
		viz[y]=1;
		}
		else p--;
	}
}
int main()
{
	int i,comp=0;
	citire();
	
	for(i=1;i<=n;i++)
		if(viz[i]==0) {comp++;dfs(i);}
		g<<comp;
}