public static void main ( String args [ ] ) throws IOException {
  Reader in = new Reader ( ) ;
  int n = in . nextInt ( ) ;
  int n1 = in . nextInt ( ) ;
  int n2 = in . nextInt ( ) ;
  long [ ] A = new long [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) A [ i ] = in . nextLong ( ) ;
  new MergeSortLong ( ) . sort ( A , 0 , n - 1 ) ;
  long [ ] B = new long [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) B [ i ] = A [ n - 1 - i ] ;
  long [ ] sum = new long [ n ] ;
  sum [ 0 ] = B [ 0 ] ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) sum [ i ] = sum [ i - 1 ] + B [ i ] ;
  double ans = 0.0d ;
  long nn1 = n1 * sum [ n2 - 1 ] + n2 * ( sum [ n1 + n2 - 1 ] - sum [ n2 - 1 ] ) ;
  long nn2 = n2 * sum [ n1 - 1 ] + n1 * ( sum [ n1 + n2 - 1 ] - sum [ n1 - 1 ] ) ;
  System . out . println ( Math . max ( nn1 , nn2 ) / ( ( double ) ( 1L * n1 * n2 ) ) ) ;
}

public static void main ( String args [ ] ) throws IOException { Reader in = new Reader ( ) ; int n = in . nextInt ( ) ; int n1 = in . nextInt ( ) ; int n2 = in . nextInt ( ) ; long [ ] A = new long [ n ] ; for ( int i = 0 ; i < n ; i ++ ) A [ i ] = in . nextLong ( ) ; new MergeSortLong ( ) . sort ( A , 0 , n - 1 ) ; long [ ] B = new long [ n ] ; for ( int i = 0 ; i < n ; i ++ ) B [ i ] = A [ n - 1 - i ] ; long [ ] sum = new long [ n ] ; sum [ 0 ] = B [ 0 ] ; for ( int i = 1 ; i < n ; i ++ ) sum [ i ] = sum [ i - 1 ] + B [ i ] ; double ans = 0.0d ; long nn1 = n1 * sum [ n2 - 1 ] + n2 * ( sum [ n1 + n2 - 1 ] - sum [ n2 - 1 ] ) ; long nn2 = n2 * sum [ n1 - 1 ] + n1 * ( sum [ n1 + n2 - 1 ] - sum [ n1 - 1 ] ) ; System . out . println ( Math . max ( nn1 , nn2 ) / ( ( double ) ( 1L * n1 * n2 ) ) ) ; }
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