import java.io.*;
import java.util.*;

public class bottom
{

public static void main( String args[] ) throws Exception
{
BufferedReader in=new BufferedReader(new FileReader("bottom.in") );
String S = "";
StringTokenizer T;
boolean M[][];
boolean L[];
int v=-1, e=0;
boolean first;

while (true)
   {
   S = in.readLine();
   if (S.compareTo("0")==0) break;
   if (v!=-1) System.out.println("");
   T = new StringTokenizer( S );
   v = Integer.parseInt(T.nextToken());
   e = Integer.parseInt(T.nextToken());
   M = new boolean[v][v];
   for(int i=0; i<v; i++)
      for(int j=0; j<v; j++)
         M[i][j]=(i==j);
   T = new StringTokenizer(in.readLine() );
   for (int i=0; i<e; i++)
       {
       M[Integer.parseInt(T.nextToken())-1][Integer.parseInt(T.nextToken())-1]=true;
       }

   for (int i=0; i<v; i++)

   M = THuelle(M,v);

   L= new boolean[v];
   for (int i=0; i<v; i++)
       L[i]=true;
   for (int i=0; i<v; i++)
       for (int j=0; j<v; j++)
          {
          L[j]=L[j] && M[i][j];
	  L[i]=L[i] && M[j][i];
          }
   first=true;
   for (int i=0; i<v; i++)
       {
       System.out.print( first ? "" : " ");
       first = first && !L[i];
       System.out.print( L[i] ? ((i+1)+"") : "" );
       }

   }//endwhile

   if (v!=-1)  System.out.println("");

}//endmain

public static boolean[][] THuelle(boolean[][] M, int v)
{
      for (int i=0; i<v; i++)
         for (int j=0; j<v; j++)
	     for (int k=0; k<v; k++) //Warshall - Transitive Hülle
	         {
		 if (M[i][k] && M[k][j])
                     M[i][j]=true;
		 if (M[i][j]) break;
		 }
return M;
}


}//endclass