total no of pages in spool

i need to print  total no of pages in the classical report output in the spool .

i have implemented the below code but its calculating incorrect page numbers.

CALL FUNCTION 'DISPLAY_PAGENUMBER'

EXPORTING

    LINES_TOTAL        = LW_TOT_LINES_5

    LINES_LOOP         = '7'

IMPORTING

    PAGES_TOTAL        = lw_tot_pages.

also i tried the code

DESCRIBE TABLE GINT_ALV_A  LINES LW_TOT_LINES_1.

DESCRIBE TABLE GINT_ALV_B  LINES LW_TOT_LINES_2.

DESCRIBE TABLE GINT_ALV_C  LINES LW_TOT_LINES_3.

DESCRIBE TABLE GINT_ALV_D  LINES LW_TOT_LINES_4.

LW_TOT_LINES_5 = LW_TOT_LINES_1 + LW_TOT_LINES_2 + LW_TOT_LINES_3 + LW_TOT_LINES_4 + 35.

**************

LW_TEMP = LW_TOT_LINES_5 / 30.

lw_tot_pages = trunc( LW_TEMP ).

*temp = frac( temp ).

if LW_TEMP > 0.

lw_tot_pages = lw_tot_pages + 1.

endif.

but even the above code is not working.

please help