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

class intList{

    intList(){
	this.data = -1;
	this.next = null;
    }

    intList( int data ){
	this.data = data;
	this.next = null;
    }

    void add( int n ){
	if( this.data == -1 )this.data = n;
	else if( this.next == null )this.next = new intList(n);
	else this.next.add(n);
    }

    boolean contains( int n ){
	if( this.data == n )return true;
	if( this.next == null )return false;
	return this.next.contains(n);
    }

    int elements(){
	if( this.next == null )return 1;
	return 1+this.next.elements();
    }
    
    int[] toArray(){
	int n = this.elements();
	int[] ret = new int[n];
	intList help = this;
	boolean written = false;

	for( int i=0; i<n; i++){
	    if(help.data != -1){
		ret[i] = help.data;
		written = true;
	    }
	    help = help.next;
	}
	if( written )return ret;
	else return null;
    }

    public String toString(){
	if( this.data == -1 )return "none";
	if( this.next == null )return ("" + this.data);
	return this.data + " " + this.next.toString();
    }

    int data;
    intList next;
}

class queue{
    int data[];
    int first;
    int last;
    public int check[][];

    queue( int max ){
	this.data=new int[max];
	this.check = new int[max][max];
	this.first=0;
	this.last=0;
    }
    
    public void append( int n, int check ){
	this.data[this.last++] = n;
	this.check[check][n] = 1;
    }

    public int get(){
	return this.data[this.first++];
    }

    public boolean empty(){
	return first==last;
    }

    public String toString(){
	String buffer = "";
	for( int n=first; n<last; n++ )buffer += this.data[n]+", ";
	return buffer;
    }

}

public class bottom{

    static boolean reaches( int[][] edges, int source, int dest ){
	queue queue = new queue(100);
	queue.append(source, source);
	//	System.out.println( "Searching Path from " + source + " to " + dest );
	
	while( !queue.empty() ){
	    //	    System.out.println( source + " -> " + queue.toString() );
	    int node = queue.get();
	    if( node == dest )return true;
	    for( int n=0; n< edges.length; n++ )if( edges[n][0] == node ){
		if( queue.check[node][edges[n][1]] == 1 )return false;
		queue.append( edges[n][1], node );
		//		System.out.println( "Appending " + edges[n][1] + " from: " + source);
	    }
	    
	}
	
	return false;
    }
    
    static intList sinks( int nodes, int[][] edges ){
	intList list[] = new intList[nodes+1];
	intList sinks = new intList();

 	for( int n=1; n<=nodes; n++ ){
	    list[n] = new intList();
	    for( int i=0; i<edges.length; i++ )
		if( edges[i][0] == n ){
		    list[n].add( edges[i][1] );
		}
	}

	for( int n=1; n<=nodes; n++){
	    int[] conns = list[n].toArray();
	    //System.out.println( n + ": " + list[n].toString() );

	    boolean sink = true;
	    if( conns != null)
		for( int i=0; i<conns.length; i++ ){
		    //ARGH- auch transitiv suchen...
		    //if( !list[conns[i]-1].contains(n) )sink = false;
		    if( !reaches( edges, conns[i], n ) )sink = false; 
		}
	   

	    if( sink ){
		sinks.add( n );
		//		System.out.println( n + " is a sink");
	    }
	}

	return sinks;

    }

    public static void main( String[] args ) throws Exception{
	BufferedReader br = new BufferedReader( new FileReader( "bottom.in" ) );
	
	String line;
	while( (line = br.readLine()) != null ){
	    if( br == null || line.equals("0") )System.exit(-1);
	    
	    int nnodes = Integer.parseInt( line.substring( 0, line.indexOf( " " ) ) );
	    int nedges = Integer.parseInt( line.substring( line.indexOf( " " ) + 1) );
	    
	    int[][] edges = new int[nedges][2];
	    
	    int n=0;
	    
	    line = br.readLine();
	    StringTokenizer tok = new StringTokenizer( line, " " );
	    while( tok.hasMoreTokens() ){
		edges[n/2][n%2] = Integer.parseInt( tok.nextToken() );
		n++;
	    }

	    intList sinks = sinks( nnodes, edges );

	    //	    System.out.println( "Graph has " +nnodes + " Nodes and " +nedges + " Edges" );
	    System.out.println( /*"Sinks are " +*/ sinks.toString() );
	}
	/*	queue q = new queue(10);
	q.append(1);
	q.append(3);
	q.append(4);
	q.get();
	System.out.println( q.toString() );*/
    }
}