public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int [ ] a = new int [ n ] ;
  a [ 0 ] = 0 ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    a [ i ] = sc . nextInt ( ) ;
  }
  sc . close ( ) ;
  win = new ArrayList [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    win [ i ] = new ArrayList < Integer > ( ) ;
  }
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    win [ a [ i ] - 1 ] . add ( i ) ;
  }
  dp = new int [ n ] ;
  solve ( 0 ) ;
  System . out . println ( dp [ 0 ] - 1 ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int [ ] a = new int [ n ] ; a [ 0 ] = 0 ; for ( int i = 1 ; i < n ; i ++ ) { a [ i ] = sc . nextInt ( ) ; } sc . close ( ) ; win = new ArrayList [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { win [ i ] = new ArrayList < Integer > ( ) ; } for ( int i = 1 ; i < n ; i ++ ) { win [ a [ i ] - 1 ] . add ( i ) ; } dp = new int [ n ] ; solve ( 0 ) ; System . out . println ( dp [ 0 ] - 1 ) ; }
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