#include<iostream>
#include<cstring>
using namespace std;
const int N=102;
int map[N][N],tmap[N][N];
void warshell(int n)
{
	int i,j,k;
	for(i=1;i<=n;++i)
		for(j=1;j<=n;++j)
		{
			for(k=1;k<=n;++k)
				tmap[i][j]=tmap[i][j] || (map[i][k] && map[k][j]);
			tmap[i][j]=(map[i][j] || tmap[i][j]);
		}
}
int main()
{
	int n,i,j,k,m;
	memset(map,0,sizeof(map));
	memset(tmap,0,sizeof(tmap));
	scanf("%d%d",&n,&m);
	for(i=0;i<m;++i)
	{
		scanf("%d%d",&j,&k);
		map[j][k]=1;
	}
	warshell(n);
	int ans=0,tmp;
	for(i=1;i<=n;++i)
	{
		tmp=0;
		for(j=1;j<=n;++j)
			if(i!=j)
				if(tmap[i][j] || tmap[j][i])
					++tmp;
				if(tmp==n-1)
				++ans;
	}
	printf("%d\n",ans);
	return false;
}