public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int sum = 0 ;
  Map < Integer , Integer > map = new HashMap < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int a = sc . nextInt ( ) ;
    if ( a == i ) sum ++ ;
    else map . put ( i , a ) ;
  }
  List < Integer > list = new ArrayList < > ( map . keySet ( ) ) ;
  boolean tt = false ;
  for ( Integer integer : list ) {
    int v1 = map . get ( integer ) ;
    int v2 = map . get ( v1 ) ;
    if ( v2 == integer ) {
      tt = true ;
      break ;
    }
  };
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int sum = 0 ; Map < Integer , Integer > map = new HashMap < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { int a = sc . nextInt ( ) ; if ( a == i ) sum ++ ; else map . put ( i , a ) ; } List < Integer > list = new ArrayList < > ( map . keySet ( ) ) ; boolean tt = false ; for ( Integer integer : list ) { int v1 = map . get ( integer ) ; int v2 = map . get ( v1 ) ; if ( v2 == integer ) { tt = true ; break ; } } ; }
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