public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int m = sc . nextInt ( ) ;
  List < ArrayList < Integer >> connect = new ArrayList < ArrayList < Integer >> ( ) ;
  for ( int i = 0 ;
  i < n + 1 ;
  i ++ ) {
    connect . add ( new ArrayList < Integer > ( ) ) ;
  }
  for ( int i = 0 ;
  i < m ;
  i ++ ) {
    int a = sc . nextInt ( ) ;
    int b = sc . nextInt ( ) ;
    connect . get ( a ) . add ( b ) ;
    connect . get ( b ) . add ( a ) ;
  }
  boolean taken [ ] = new boolean [ n + 1 ] ;
  taken [ 1 ] = true ;
  LinkedList < Integer > ans = new LinkedList < Integer > ( ) ;
  ans . add ( 1 ) ;
  extend ( ans , connect , taken , false ) ;
  extend ( ans , connect , taken , true ) ;
  System . out . println ( ans . size ( ) ) ;
  StringBuilder sb = new StringBuilder ( ) ;
  for ( Integer i : ans ) {
    sb . append ( i ) ;
    sb . append ( ' ' ) ;
  }
  sb . deleteCharAt ( sb . length ( ) - 1 ) ;
  System . out . println ( sb ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int m = sc . nextInt ( ) ; List < ArrayList < Integer > > connect = new ArrayList < ArrayList < Integer > > ( ) ; for ( int i = 0 ; i < n + 1 ; i ++ ) { connect . add ( new ArrayList < Integer > ( ) ) ; } for ( int i = 0 ; i < m ; i ++ ) { int a = sc . nextInt ( ) ; int b = sc . nextInt ( ) ; connect . get ( a ) . add ( b ) ; connect . get ( b ) . add ( a ) ; } boolean taken [ ] = new boolean [ n + 1 ] ; taken [ 1 ] = true ; LinkedList < Integer > ans = new LinkedList < Integer > ( ) ; ans . add ( 1 ) ; extend ( ans , connect , taken , false ) ; extend ( ans , connect , taken , true ) ; System . out . println ( ans . size ( ) ) ; StringBuilder sb = new StringBuilder ( ) ; for ( Integer i : ans ) { sb . append ( i ) ; sb . append ( ' ▁ ' ) ; } sb . deleteCharAt ( sb . length ( ) - 1 ) ; System . out . println ( sb ) ; }
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