public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int m = sc . nextInt ( ) ;
  ArrayList < Integer > [ ] graph = new ArrayList [ n + 1 ] ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) {
    graph [ i ] = new ArrayList < Integer > ( ) ;
  }
  for ( int i = 0 ;
  i < m ;
  i ++ ) {
    int a = sc . nextInt ( ) ;
    int b = sc . nextInt ( ) ;
    graph [ a ] . add ( b ) ;
    graph [ b ] . add ( a ) ;
  }
  HashSet < Integer > set = new HashSet < > ( ) ;
  ArrayList < Integer > list = new ArrayList < > ( ) ;
  int idx = 1 ;
  boolean flag = false ;
  list . add ( idx ) ;
  set . add ( idx ) ;
  while ( ! flag ) {
    flag = true ;
    for ( int x : graph [ idx ] ) {
      if ( ! set . contains ( x ) ) {
        flag = false ;
        idx = x ;
        list . add ( idx ) ;
        set . add ( idx ) ;
        break ;
      }
    }
  }
  flag = false ;
  idx = 1 ;
  while ( ! flag ) {
    flag = true ;
    for ( int x : graph [ idx ] ) {
      if ( ! set . contains ( x ) ) {
        flag = false ;
        idx = x ;
        list . add ( 0 , idx ) ;
        set . add ( idx ) ;
        break ;
      }
    }
  }
  StringBuilder sb = new StringBuilder ( ) ;
  sb . append ( list . size ( ) ) . append ( "\n" ) ;
  for ( int i = 0 ;
  i < list . size ( ) ;
  i ++ ) {
    if ( i != 0 ) {
      sb . append ( " " ) ;
    }
    sb . append ( list . get ( i ) ) ;
  }
  System . out . println ( sb ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int m = sc . nextInt ( ) ; ArrayList < Integer > [ ] graph = new ArrayList [ n + 1 ] ; for ( int i = 1 ; i <= n ; i ++ ) { graph [ i ] = new ArrayList < Integer > ( ) ; } for ( int i = 0 ; i < m ; i ++ ) { int a = sc . nextInt ( ) ; int b = sc . nextInt ( ) ; graph [ a ] . add ( b ) ; graph [ b ] . add ( a ) ; } HashSet < Integer > set = new HashSet < > ( ) ; ArrayList < Integer > list = new ArrayList < > ( ) ; int idx = 1 ; boolean flag = false ; list . add ( idx ) ; set . add ( idx ) ; while ( ! flag ) { flag = true ; for ( int x : graph [ idx ] ) { if ( ! set . contains ( x ) ) { flag = false ; idx = x ; list . add ( idx ) ; set . add ( idx ) ; break ; } } } flag = false ; idx = 1 ; while ( ! flag ) { flag = true ; for ( int x : graph [ idx ] ) { if ( ! set . contains ( x ) ) { flag = false ; idx = x ; list . add ( 0 , idx ) ; set . add ( idx ) ; break ; } } } StringBuilder sb = new StringBuilder ( ) ; sb . append ( list . size ( ) ) . append ( " \n " ) ; for ( int i = 0 ; i < list . size ( ) ; i ++ ) { if ( i != 0 ) { sb . append ( " ▁ " ) ; } sb . append ( list . get ( i ) ) ; } System . out . println ( sb ) ; }
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