public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  n = sc . nextInt ( ) ;
  k = sc . nextInt ( ) ;
  dp = new double [ n + 1 ] [ k + 2 ] [ 2 ] ;
  for ( int i = 0 ;
  i < k + 1 ;
  i ++ ) {
    dp [ n ] [ i ] [ 1 ] = 1 ;
  }
  for ( int i = n - 1 ;
  i >= 0 ;
  i -- ) {
    for ( int j = 0 ;
    j < k + 1 ;
    j ++ ) {
      for ( int l = 0 ;
      l < 2 ;
      l ++ ) {
        double p = 1.0 / ( i + 1 ) ;
        double r = ( 1.0 - p ) * dp [ i + 1 ] [ j ] [ l ] + p * Math . max ( dp [ i + 1 ] [ j + 1 ] [ 1 ] , dp [ i + 1 ] [ j ] [ 0 ] ) ;
        dp [ i ] [ j ] [ l ] = r ;
      }
    }
  }
  System . out . println ( dp [ 0 ] [ 0 ] [ 0 ] ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; n = sc . nextInt ( ) ; k = sc . nextInt ( ) ; dp = new double [ n + 1 ] [ k + 2 ] [ 2 ] ; for ( int i = 0 ; i < k + 1 ; i ++ ) { dp [ n ] [ i ] [ 1 ] = 1 ; } for ( int i = n - 1 ; i >= 0 ; i -- ) { for ( int j = 0 ; j < k + 1 ; j ++ ) { for ( int l = 0 ; l < 2 ; l ++ ) { double p = 1.0 / ( i + 1 ) ; double r = ( 1.0 - p ) * dp [ i + 1 ] [ j ] [ l ] + p * Math . max ( dp [ i + 1 ] [ j + 1 ] [ 1 ] , dp [ i + 1 ] [ j ] [ 0 ] ) ; dp [ i ] [ j ] [ l ] = r ; } } } System . out . println ( dp [ 0 ] [ 0 ] [ 0 ] ) ; }
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