#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;
int n,m,q[103][103],answer=0;
int main()
{
    freopen ("contest.in","r",stdin);
    freopen ("contest.out","w",stdout);
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++)
    {
        for (int j=1;j<=n;j++)
        {
            q[i][j]=-1;
        }
    }
    for (int k=0;k<m;k++)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        q[a][b]=1;
    }
    for (int k=1;k<=n;k++)
        for (int i=1;i<=n;i++)
            for (int j=1;j<=n;j++)
                if (q[i][k]!=-1&&q[k][j]!=-1)
                    q[i][j]=q[i][k]+q[k][j];
    for (int o=1;o<=n;o++)
    {
        int c=0;
        for (int u=1;u<=n;u++)
        {
            if (o!=u)
            {
                if (q[o][u]!=-1)
                {
                    c++;
                }
                else
                {
                    if (q[u][o]!=-1)
                        c++;
                }
            }
        }
        if (c>=n-1)
            answer++;
    }
    cout<<answer;
    return 0;
}