#include <iostream>
#include<algorithm>
#include<vector>
using namespace std;
vector<int>val;
int main() {
// your code goes here
while(1)
{
int n,e,x,y,i,j;
cin>>n>>e;
if(n==0)
break;
int vis[n+1];
int a[n+1][n+1];
val.clear();
for(i=0;i<n;i++)
{
vis[i]=0;
for(j=0;j<n;j++)
a[i][j]=0;
}
while(e--)
{
cin>>x>>y;
a[x-1][y-1]=1;
}
for(i=0;i<n;i++)
{
for(j=0;j<n;j++)
{
if(a[i][j]==1 && a[j][i]==1)
val.push_back(i);
}
}
for(i=0;i<(int)val.size();i++)
{
vis[val[i]]=1;
}
for(i=0;i<n;i++)
{
int f=0;
if(vis[i]==0)
{
//cout<<" i = "<<i<<endl;
for(j=0;j<n;j++)
{
if(a[i][j]!=0)
{
f=1; break;
}
}
if(f==0)
val.push_back(i);
}
}
if(val.size()==0)
cout<<endl;
else
{
for(i=0;i<(int)val.size();i++)
{
val[i]=val[i]+1;
}
sort(val.begin(), val.end());
for(i=0;i<(int)val.size();i++)
cout<<val[i]<<" ";
cout<<endl;
}
}
return 0;
}
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