#include<fstream>
#include<iostream>
using namespace std;
#define max 100001
int n,*a[max],v[max],m,nrc;
void read()
{
	int m,i,j;
	int *grad=new int [n+1];
	for(int i=1;i<=n;i++)
		grad[i]=0;
	ifstream fin("dfs.in");
	fin>>n>>m;
	for(;m;--m)
	{
		fin>>i>>j;
		grad[i]++;
	}
	fin.close();
	fin.open("dfs.in");
	fin>>n>>m;
	for(int i=1;i<=n;i++)
		{
			a[i]=new int [grad[i]+1];
			a[i][0]=0;
		}
	delete [] grad;
	for(;m;--m)
	{
		fin>>i>>j;
		a[i][++a[i][0]]=j;
	}
}
void dfs(int i)
{
	v[i]=1;
	for(int k=1;k<=a[i][0];k++)
		if(v[k]==0)
		{
			//t[k]=i;
			dfs(k);
		}
}
int main()
{
	read();
	int nrc=0;
	for(int i=1;i<=n;i++)
		if(v[i]==0)
			dfs(i),nrc++;
	FILE *fout=fopen("dfs.out","w");
	fprintf(fout,"%d ",nrc);
	return 0;
}