subroutine dfftb(n, r, wsave)
use fftpack_kind, only: dp => rk
implicit none
integer, intent(in) :: n
real(dp), intent(inout) :: r(*)
real(dp), intent(inout) :: wsave(*)
if (n == 1) return
call rfftb1(n, r, wsave, wsave(n + 1), wsave(2*n + 1))
end subroutine dfftb
