public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  ArrayList < Integer > a = new ArrayList < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) a . add ( sc . nextInt ( ) ) ;
  Collections . reverse ( a ) ;
  Set < Integer > s = new LinkedHashSet < Integer > ( ) ;
  s . addAll ( a ) ;
  a . clear ( ) ;
  a . addAll ( s ) ;
  Collections . reverse ( a ) ;
  s . clear ( ) ;
  s . addAll ( a ) ;
  Iterator < Integer > i = s . iterator ( ) ;
  System . out . println ( s . size ( ) ) ;
  while ( i . hasNext ( ) ) {
    System . out . print ( i . next ( ) + " " ) ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; ArrayList < Integer > a = new ArrayList < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) a . add ( sc . nextInt ( ) ) ; Collections . reverse ( a ) ; Set < Integer > s = new LinkedHashSet < Integer > ( ) ; s . addAll ( a ) ; a . clear ( ) ; a . addAll ( s ) ; Collections . reverse ( a ) ; s . clear ( ) ; s . addAll ( a ) ; Iterator < Integer > i = s . iterator ( ) ; System . out . println ( s . size ( ) ) ; while ( i . hasNext ( ) ) { System . out . print ( i . next ( ) + " ▁ " ) ; } }
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