#include<bits/stdc++.h>
using namespace std;
int n,m;
bool f[105][105];
int main()
{
	    freopen("contest.in","r",stdin);
    freopen("contest.out","w",stdout);
	scanf("%d%d",&n,&m);
	for (int i=1;i<=m;i++)
	{
		int x,y;
		scanf("%d%d",&x,&y);
		f[x][y]=true;
	}
	for (int k=1;k<=n;k++)
		for (int x=1;x<=n;x++)
			for (int y=1;y<=n;y++)
				f[x][y]=(f[x][k]&&f[k][y])||f[x][y];
	int Ans=0;
	for (int i=1;i<=n;i++)
	{
		int cnt=0;
		for (int j=1;j<=n;j++)
			if (f[i][j]||f[j][i]) 
			cnt++;
		if (cnt==n-1) 
		Ans++;
	}
	printf("%d\n",Ans);
	return 0;
}