contains
   pure subroutine sort(A, len)
      integer, intent(inout)  :: A(:)
      integer, intent(in)     :: len
      integer                 :: i, j, z

      do i = 1, len
         do j = 1, len - i
            if(A(j) < A(j+1)) then
               z = A(j+1)
               A(j+1) = A(j)
               A(j) = z
            end if
         end do
      end do

   end subroutine