### The Bottom of a Graph

#### Problem Description

We will use the following (standard) definitions from graph theory. Let *V* be a nonempty and finite set, its elements being called vertices (or nodes). Let *E* be a subset of the Cartesian product *V×V*, its elements being called edges. Then *G=(V,E)* is called a directed graph.

Let *n* be a positive integer, and let *p=(e _{1},...,e_{n})* be a sequence of length

*n*of edges

*e*such that

_{i}∈E*e*for a sequence of vertices

_{i}=(v_{i},v_{i+1})*(v*. Then

_{1},...,v_{n+1})*p*is called a path from vertex

*v*to vertex

_{1}*v*in

_{n+1}*G*and we say that

*v*is reachable from

_{n+1}*v*, writing

_{1}*(v*.

_{1}→v_{n+1})Here are some new definitions. A node *v* in a graph *G=(V,E)* is called a sink, if for every node *w* in *G* that is reachable from *v*, *v* is also reachable from *w*. The bottom of a graph is the subset of all nodes that are sinks, i.e., *bottom(G)={v∈V|∀w∈V:(v→w)⇒(w→v)}*. You have to calculate the bottom of certain graphs.

#### Input

*G*. Each test case starts with an integer number

*v*, denoting the number of vertices of

*G=(V,E)*, where the vertices will be identified by the integer numbers in the set

*V={1,...,v}*. You may assume that

*1<=v<=5000*. That is followed by a non-negative integer

*e*and, thereafter,

*e*pairs of vertex identifiers

*v*with the meaning that

_{1},w_{1},...,v_{e},w_{e}*(v*. There are no edges other than specified by these pairs. The last test case is followed by a zero.

_{i},w_{i})∈E#### Output

For each test case output the bottom of the specified graph on a single line. To this end, print the numbers of all nodes that are sinks in sorted order separated by a single space character. If the bottom is empty, print an empty line.

#### Sample Input

3 3 1 3 2 3 3 1 2 1 1 2 0

#### Sample Output

1 3 2