public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  PrintWriter out = new PrintWriter ( System . out ) ;
  int houses = in . nextInt ( ) ;
  int [ ] colors = new int [ houses ] ;
  for ( int i = 0 ;
  i < houses ;
  i ++ ) colors [ i ] = in . nextInt ( ) ;
  int distanceEnd = 0 ;
  for ( int i = 0 ;
  i < houses - 1 ;
  i ++ ) {
    if ( colors [ i ] != colors [ houses - 1 ] ) {
      distanceEnd = Math . abs ( ( houses - 1 ) - i ) ;
      break ;
    }
  }
  int distanceBeg = 0 ;
  for ( int i = houses - 1 ;
  i > - 1 ;
  i -- ) {
    if ( colors [ i ] != colors [ 0 ] ) {
      distanceBeg = Math . abs ( i ) ;
      break ;
    }
  }
  out . print ( Math . max ( distanceBeg , distanceEnd ) ) ;
  out . close ( ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; PrintWriter out = new PrintWriter ( System . out ) ; int houses = in . nextInt ( ) ; int [ ] colors = new int [ houses ] ; for ( int i = 0 ; i < houses ; i ++ ) colors [ i ] = in . nextInt ( ) ; int distanceEnd = 0 ; for ( int i = 0 ; i < houses - 1 ; i ++ ) { if ( colors [ i ] != colors [ houses - 1 ] ) { distanceEnd = Math . abs ( ( houses - 1 ) - i ) ; break ; } } int distanceBeg = 0 ; for ( int i = houses - 1 ; i > - 1 ; i -- ) { if ( colors [ i ] != colors [ 0 ] ) { distanceBeg = Math . abs ( i ) ; break ; } } out . print ( Math . max ( distanceBeg , distanceEnd ) ) ; out . close ( ) ; }
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