I want to find out total no of pages of a report output.  This no I have to print in TOP-OF-PAGE event.

Check this below code. You will get the clear idea.

  REPORT YJAM_WA no standard page heading line-count 60(5).

  data: v_totpage type i.
  data: v_temp(3) type c.
  Start-of-selection.
   do 100 times.
       write:/ sy-index.
   enddo.

  end-of-selection.
   v_temp = v_totpage.
   do v_totpage times.
      read line 1 of page sy-index.
      replace '@@@' in sy-lisel with  v_temp.
      modify line 1 of page sy-index.
   enddo.

  top-of-page.
   write:/60 'page', sy-pagno, '/','@@@'.
   v_totpage = sy-pagno.
 

Here is  a sample:

* zlines number of lines in the table
* sy-srows number of lines in screen
* sy-cpage current page
* zpages total number of pages type i
* temp temporary number type f
describe table itab lines zlines.
temp = zlines / sy-srows.
zpages = trunc( temp ).
temp = frac( temp ).
if temp > 0.
zpages = zpages + 1.
endif.
* zpages is the number of pages
write: /'Page ',sy-cpage, ' of ', zpages.

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