public static void main ( String [ ] args ) throws Exception {
  Scanner sc = new Scanner ( System . in ) ;
  int n = Integer . parseInt ( sc . next ( ) ) ;
  int [ ] a = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    a [ i ] = Integer . parseInt ( sc . next ( ) ) - 1 ;
  }
  int m = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) m = Math . max ( m , a [ i ] ) ;
  boolean [ ] use = new boolean [ m + 1 ] ;
  int s = 1 ;
  int t = 0 ;
  use [ a [ 0 ] ] = true ;
  long ret = 1 ;
  while ( s < n ) {
    while ( t < s && use [ a [ s ] ] ) {
      use [ a [ t ] ] = false ;
      t ++ ;
    }
    while ( s < n && ! use [ a [ s ] ] ) {
      use [ a [ s ] ] = true ;
      s ++ ;
    }
    ret = Math . max ( ret , s - t ) ;
  }
  System . out . println ( ret ) ;
}

public static void main ( String [ ] args ) throws Exception { Scanner sc = new Scanner ( System . in ) ; int n = Integer . parseInt ( sc . next ( ) ) ; int [ ] a = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { a [ i ] = Integer . parseInt ( sc . next ( ) ) - 1 ; } int m = 0 ; for ( int i = 0 ; i < n ; i ++ ) m = Math . max ( m , a [ i ] ) ; boolean [ ] use = new boolean [ m + 1 ] ; int s = 1 ; int t = 0 ; use [ a [ 0 ] ] = true ; long ret = 1 ; while ( s < n ) { while ( t < s && use [ a [ s ] ] ) { use [ a [ t ] ] = false ; t ++ ; } while ( s < n && ! use [ a [ s ] ] ) { use [ a [ s ] ] = true ; s ++ ; } ret = Math . max ( ret , s - t ) ; } System . out . println ( ret ) ; }
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