public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int m = sc . nextInt ( ) ;
  graph = new ArrayList [ n + 1 ] ;
  for ( int i = 0 ;
  i <= n ;
  i ++ ) graph [ i ] = new ArrayList < > ( ) ;
  for ( int j = 0 ;
  j < m ;
  j ++ ) {
    int a = sc . nextInt ( ) , b = sc . nextInt ( ) ;
    graph [ a ] . add ( b ) ;
    graph [ b ] . add ( a ) ;
  }
  LinkedList < Integer > ans = helper ( n ) ;
  PrintWriter out = new PrintWriter ( System . out ) ;
  out . println ( ans . size ( ) ) ;
  while ( ans . size ( ) > 0 ) {
    out . print ( ans . poll ( ) ) ;
    out . print ( " " ) ;
  }
  out . flush ( ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int m = sc . nextInt ( ) ; graph = new ArrayList [ n + 1 ] ; for ( int i = 0 ; i <= n ; i ++ ) graph [ i ] = new ArrayList < > ( ) ; for ( int j = 0 ; j < m ; j ++ ) { int a = sc . nextInt ( ) , b = sc . nextInt ( ) ; graph [ a ] . add ( b ) ; graph [ b ] . add ( a ) ; } LinkedList < Integer > ans = helper ( n ) ; PrintWriter out = new PrintWriter ( System . out ) ; out . println ( ans . size ( ) ) ; while ( ans . size ( ) > 0 ) { out . print ( ans . poll ( ) ) ; out . print ( " ▁ " ) ; } out . flush ( ) ; }
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