subroutine swap(a, i, j)
      integer a(*), i, j, temp
      temp = a(i)
      a(i) = a(j)
      a(j) = temp
      end

      subroutine sort (a, n)
      integer a(n), gap, j, temp
      logical swapped
      gap = n
      do
         gap = (gap * 10) / 13
         if (gap .eq. 9 .or. gap .eq. 10) gap = 11
         if (gap .lt. 1) gap = 1
         swapped = .false.
         do i = 1, n - gap
            j = i + gap
            if (a(i) .gt. a(j)) then
               call swap(a, i, j)
               swapped = .true.
            end if            
         end do
         if (gap .eq. 1 .and. .not. swapped) return
      end do
      end

      program combsort
      integer a(10)
      data a /1, 6, 5, 3, 8, 9, 7, 2, 4, 0/
      call sort(a, 10)
      write (*, *) a
      end