!!!**********************************************************************
program main
!!!**********************************************************************  

  integer   :: n, d, x
  ! real      ::
  ! character ::
  
!!!----------------------------------------------------------------------

  read ( unit = *, fmt = * ) n, d

  
  x = ceiling ( real ( 2 * d + 1 ) / real ( n ) )

  if ( mod ( 2 * d + 1 , n ) /= 0 ) then

     x = x + 1

  end if
    
  ! if ( mod( n, 2*d+1 ) /= 0 ) then

  !    x = x + 1

  ! end if
  
  print "(i0)", x  
  
!!!**********************************************************************  
end program main
!!!**********************************************************************
